Tumors

Adipose (Lipoma) Tumors

Lipomas are common, usually harmless, tumors of fat that usually show up as a lump under the skin in middle-aged to older animals. Some pets will develop these tumors in their armpit region, between their legs, or around the neck, which can cause discomfort and/or lameness. You may see your pet exhibit an irregular gait, and/or reluctance to stand, walk upstairs, or go for their normal walks. This handout reviews the diagnosis, treatment, and prognosis of lipomas.

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Adrenal Cortex Tumors

Endocrine glands produce specialized chemicals called "hormones". These regulate and integrate many activities to maintain internal stability of the body.

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Adrenal Medulla Tumors

The adrenal medulla is responsible for producing hormones such as epinephrine, norepinephrine, and dopamine. An adrenal medulla tumor is the result of abnormal, uncontrolled growth of the cells that produce these hormones. These tumors may go undetected for a long time and clinical signs may be subtle. These signs could include weakness, excessive panting and restlessness, newly noted anxiety, and an increase in drinking and urination. The biggest concern with these tumors is their ability to continue to grow and invade local tissues, which can make surgical removal difficult or impossible.

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Anal Sac Tumors

Anal sac tumors grow quickly and have a moderate risk of spreading to other parts of the body. Depending on the tumor’s size, your pet could develop signs of straining to defecate or produce thin ribbon-like stool. An increased calcium level in the blood is consistent with anal sac tumors, which can cause other signs and result in kidney failure. The best and most well-described local treatment for the primary tumor is surgery. Radiation and chemotherapy may be considered if there is evidence of spread.

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Soft Tissue Sarcomas

Soft tissue sarcomas are a broad category of tumors that can develop over the chest, back, side, legs, and facial tissues of your pet. The clinical signs depend on where the tumor is located and the tissues that are affected. Often, pets have a noticeable mass that is growing in size. One of the biggest concerns with soft tissue sarcomas is their ability to invade the local surrounding tissues. The most commonly pursued treatment is surgery. Chemotherapy is not usually pursued as a primary treatment unless surgery or radiation are not options for your pet based on the tumor size or location.

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Cytology, Biopsy, and Histopathology

Collecting tissue samples for cytology or histopathology allow a pathologist to often give a diagnosis of the type of mass or tumor your pet has. Samples can be obtained by fine needle aspirate or biopsy, where a piece of the mass is cut out. Based on what the mass appears like under the microscope, the pathologist can often give a prognosis of how the tumor will behave.

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Ear Canal Tumors

Ear canal tumors can be benign or malignant. Diagnosis is typically via fine needle aspiration or tissue biopsy. The treatment of choice for ear canal tumors is surgical excision. For benign tumors, complete surgical removal is curative. With malignant tumors, a CT scan is often performed prior to surgery to determine how invasive the tumor is and enable surgical planning. Total ear canal ablation and bulla osteotomy (TECA-BO) is the most common surgical option. Radiation therapy or chemotherapy may be pursued.

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Eye Tumors - Primary Intraocular Tumors

Primary intraocular tumors, aside from melanoma, are relatively uncommon. There are many different types of primary tumors, including ciliary body adenoma and adenocarcinomas, uveal schwannomas of blue-eyed dogs, feline post-traumatic ocular sarcomas, and iridociliary adenomas and adenocarcinomas. When an intraocular tumor is suspected, a referral to a veterinary ophthalmologist may be recommended. Diagnosis is usually via an abnormal ophthalmic examination and/or ophthalmic ultrasound. Surgery is often recommended, especially if the pet has symptoms that reduce quality of life. The risk of metastasis is related to the type of tumor.

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Eye Tumors - Melanoma in Cats

Ocular melanomas in cats may be benign or malignant. Malignant tumors, called diffuse iris melanomas, present as multifocal iridial pigmentation, and benign tumors, called limbal melanomas, present as a discernable limbal mass. The diagnosis of these tumors is in large part by clinical signs and tumor appearance. Treatment for diffuse iris melanomas may include close monitoring, laser surgery, iridectomy, and enucleation. As some iris melanomas progress slowly (over years) intervention may not be required for some time. Metastasis has been reported in about 60% of cases of diffuse iris melanoma, with spread most commonly to the regional lymph nodes, kidneys, liver, and lungs, but unlike other cancers, metastatic disease may not become evident for years. Treatment for limbal melanomas may include close monitoring, and surgery (with or without grafting) sometimes combined with cryosurgery, laser surgery, or radiation therapy. Enucleation is an option if the treatment is unsuccessful or the tumor regrows. Histopathology is always recommended for a definitive diagnosis.

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Eye Tumors - Melanoma in Dogs

Ocular melanomas, although rare, are the most common eye tumor in dogs. Ocular melanomas can originate from the uvea or the limbus. About 80% of uveal melanomas (and all limbal melanomas) are benign. The rate of metastasis is less than 5%. Ocular melanomas are at least in part heritable and caused by one or more genetic mutations. Uveal melanomas can become discrete, raised pigmented masses that damage the intraocular structures of the eye and cause hyphema, uveitis, and glaucoma. Limbal melanomas can invade the cornea and cause keratitis, grow outwards and cause conjunctivitis, and penetrate and damage the eye as with uveal tumors. Treatment for ocular melanomas may include close monitoring, surgery, iridectomy, laser surgery, cryotherapy, radiation therapy, and enucleation, depending on the type and size of the tumor and how it is affecting the eye. All tissues removed should be sent for histopathology for a definitive diagnosis. The overall prognosis is good.

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Eyelid, Conjunctival, and Peri-ocular Tumors

There are a number of tumors that affect the eyelids, conjunctiva, and periocular tissues. These can be benign or malignant and can lead to secondary problems such as eye infections and corneal ulcerations. Diagnosis is best achieved through complete surgical excision of the tumor, but fine needle aspiration may be pursued as an initial diagnostic. Surgery is highly recommended to provide the pet with symptomatic relief, remove the tumor, and obtain a definitive diagnosis. With malignant tumors, surgery is the mainstay of therapy, though radiation therapy is sometimes pursued in cases where surgical removal is not possible.

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Fibrosarcomas in Dogs

Fibrosarcomas are a type of soft tissue sarcoma that is common in dogs. They are most often found on the limbs and trunk of the body, but can also be found in the nasal cavity or mouth. They usually originate from the connective tissue of the skin and beneath the skin, but occasionally from the bone, causing a primary form of bone cancer. Older dogs and certain breeds (especially large breeds) are at greater risk. The clinical signs vary in relation to the size and location of the tumor, and its impact on the surrounding tissues. Fibrosarcomas are often painful. The diagnosis is most often based on tissue biopsy. Surgery is the treatment of choice for fibrosarcomas, with or without radiation and/or chemotherapy. Most tumors recur after surgery because of the degree of local invasiveness. Only about 10% of fibrosarcomas metastasize. With proper and prompt treatment, favorable outcomes are possible.

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Benign Fibrous Skin Tumors

Fibrous tumors, including hamartomas, are a group of benign tumors arising from fibrous and fibrous-like tissues. Nodular dermatofibrosis can be secondary to (or a consequence of) tumors in the kidney or uterus. Fibrous tumors can develop as the result of underlying, repeated trauma (e.g., pressure on the elbows when lying on hard surfaces and self-trauma with skin allergies). Therefore, once a diagnosis has been made, determining and understanding the underlying cause is important.

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Digestive Tract Intestinal Epithelial Tumors

Tumors of the intestinal epithelial lining include non-cancerous polyps, benign adenomas and malignant epithelial tumors (adenocarcinomas). The polyps and adenomas may be multiple and cause local obstruction.

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Digestive Tract Muscle Tumors

Muscle (called smooth muscle) and fibrous connective tissues form the framework (stroma) that holds other tissues together within the organs of the body. They enable these organs to contract and stretch as part of their function, for example in digestion of food.

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Osteosarcoma in Cats

Osteosarcomas are somewhat rare in cats and progress slowly. Osteosarcoma is very painful. The most common location where osteosarcomas develop in cats is the hindlimb. Amputation is by far the most common treatment. Chemotherapy is not generally pursued without evidence of metastasis, given the relatively long-term control with surgery alone.

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Pleural Effusion in Cats

Pleural effusion refers to the abnormal accumulation of fluid within the chest cavity. The fluid is not found within the lungs, but instead within the pleural sac, essentially meaning the lungs are floating in a chest that is full of fluid. Several conditions can cause pleural effusion, including chylothorax, heart failure, and tumors in the lungs or chest wall. Immediate treatment often requires oxygen support and the removal of the excess fluid by thoracocentesis, which can also then be tested to diagnose the cause of the pleural effusion. Treatment and prognosis vary depending on the underlying cause of the pleural effusion.

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Hepatoid Gland Tumors

Hepatoid gland tumors are a type of cancer that develop from the sebaceous (sweat) glands of the skin. The most common location for these tumors to develop is the perianal area, and the most common tumor is the perianal adenoma. Perianal adenocarcinomas, and rarely perianal epitheliomas may also occur. These tumors appear as one or more small, round, pink, hairless, slow-growing nodules around the anus, and can sometimes ulcerate and become infected. Malignant tumors can grow much bigger and faster, invade the underlying tissue, and metastasize. Diagnosis may be made by fine needle aspiration, biopsy, or full excision of the tumor. Staging is recommended for adenocarcinomas. Treatment may involve surgical removal along with neutering, cryotherapy, laser ablation, radiotherapy, chemotherapy, and occasionally hormone therapy. The prognosis is good with perianal adenomas, fair to poor with adenocarcinomas, and generally good with epitheliomas.

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Liver Tumors

Primary liver tumors in dogs and cats are rare. There are 4 types: hepatocellular tumors, bile duct tumors, neuroendocrine tumors, and sarcomas. These cancers can be massive, nodular, or diffuse in form. In dogs, most liver tumors are malignant, while in cats, most are benign. The signs of liver tumors range from being asymptomatic to having inappetence, fever, lethargy, and weight loss; and less commonly, nausea, vomiting and diarrhea; increased drinking and urination; and jaundice. Occasionally there are neurological signs, such as seizures. With tumor rupture and intrabdominal bleeding there may be weakness, collapse, and difficulty breathing. The diagnosis is based on history, clinical signs, exam findings, diagnostic imaging, and FNA or liver biopsy. A biopsy is best for a definitive diagnosis. Surgery is the treatment of choice for most primary liver tumors followed by chemotherapy. Chemoembolization is a newer treatment.

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Lung Tumors

Lung tumors are considered rare in cats and dogs. Certain breeds are more predisposed to develop pulmonary tumors than others. Not all pets with pulmonary tumors exhibit clinical signs and are often diagnosed incidentally from routine chest X-rays. Ultrasound-guided fine needle aspiration or biopsy will confirm the diagnosis. Pulmonary carcinomas have a high tendency to metastasize, so full staging is recommended. Surgery is by far the most common treatment, though radiation therapy may be considered if surgery is not possible.

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Lymphoma of the Skin

The most common forms of cutaneous lymphoma are epitheliotropic lymphoma and dermal lymphoma. No specific risk factors or causes have been identified in the development of cutaneous lymphoma. Generally, cutaneous lymphoma can appear as various-sized irritated, ulcerated, or infected patches anywhere on the skin, including the gums, nose, or lip margins. These areas may become ulcerated and bleed, or become crusted. Secondary infections are possible. By far, the most common treatment for cutaneous lymphoma is chemotherapy. Unfortunately, the response to treatment, although initially encouraging, is typically short-lived, with gradual return of the tumors.

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Lymphatic Vessel Tumors

Lymphatic tumors are rare in pets. Lymphangiomas are benign and lymphangiosarcomas are malignant and have a moderate-to-high metastatic potential. Patients with lymphatic tumors typically have severe edema because of lymphatic obstruction. These types of tumors occur more frequently in young dogs and cats. Treatment usually involves surgical excision and chemotherapy may be used as a follow-up treatment in the case of lymphangiosarcomas.

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Mammary Tumors in Cats

A mammary tumor develops because of abnormal replication of the cells that make up the breast tissue. In cats, most mammary tumors (80-96%) are malignant. Sexually intact cats have a seven-fold increased risk for mammary tumors compared to spayed cats. Detecting and treating these tumors when they are small, and prior to metastasis, provides your cat with the best chance of long-term control. Surgery is by far the best treatment and, given the high metastatic rate in these tumors, chemotherapy is typically pursued afterward.

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Benign Mammary Tumors in Dogs

Mammary tumors develop due to abnormal reproduction of the cells that make up the breast tissue. They can be benign or malignant. The incidence of these tumors is related to hormone status, specifically whether a dog is intact or has had an ovariohysterectomy, age, and breed. Because dogs can have both benign and malignant tumors at the same time, surgical removal and histopathology of all tumors are very important.

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Malignant Mammary Tumors in Dogs

There are several different types of malignant mammary tumors, with carcinomas being the most common. Carcinomas arise from epithelial (skin) cells, tubules of the mammary glands, or other cells found in the mammary chain. The size of the masses and their appearance may vary, but they are usually firm and nodular. Occasionally, the skin over the mass may ulcerate (open) and bleed, and the affected area may feel warm to the touch and become painful. Detecting and treating these tumors when they are small, and before spread has occurred, will provide your dog with the best chance for long-term control.

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Mast Cell Tumors in Cats

Mast cells are a type of white blood cell that plays a large role in allergic response through degranulation. Mast cell tumors (MCT) can occur in the skin, spleen, or gastrointestinal tract of cats. Their cause is unknown; however, many affected cats show a genetic mutation in the KIT protein involved in replication and cell division. Cutaneous MCTs most often appear as hard pale/white plaques or nodules, often around the head and they may be itchy. Splenic MCTs cause decreased appetite, weight loss, and vomiting. Intestinal MCTs may cause GI upset and bloody stools, and a mass may be palpable. Diagnosis is typically achieved via fine needle aspirate although histopathology can be used. Treatment usually requires surgical removal of the masses or the spleen. Sometimes, chemotherapy or radiation is needed.

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Mast Cell Tumors in Dogs

Mast cell tumors are most common in the skin of dogs and have a nodular, alopecic, sometimes inflamed appearance. These can be itchy and can fluctuate in size. They are generally easily diagnosed by fine needle aspirate but histopathology is needed to grade the tumor to determine the prognosis and best management. Tumors can range from lower-grade, with minimal metastasis and spread, to higher-grade, with a high risk of metastasis and local invasion. Treatment usually involves surgical removal with wide margins and, depending on complications, may require supportive treatment including chemotherapy, radiation therapy, and therapy to target the mutation that instigated the tumor.

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Nasal Tumors

Nasal tumors are an uncommon type of cancer but when they do occur, they tend to be malignant and locally aggressive. Staging can be done to determine the type of cancer and if it has affected anywhere else in the body. Treatment can be done in some cases to help relieve clinical signs, most often with radiation therapy.

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Neuroendocrine Tumors

Neuroendocrine tumors are a group of tumors that develop from the cells of the neuroendocrine system, and include insulinomas, gastrinomas, glucagonomas, carcinoids, medullary thyroid carcinomas, small-cell lung carcinomas, pheochromocytomas, chemodectomas, and Merkel cell carcinomas. Some of these tumors are functional, while others are non-functional. The signs of disease in dogs and cats depend on the type of growth, location of the tumor, its size, the degree of infiltration in the surrounding tissues, whether it has metastasized, and whether it is functional. A definitive diagnosis requires tissue biopsy and histopathology, often with histochemical staining and electron microscopy. Staging is highly recommended for these tumors. Treatment may involve surgery, chemotherapy, radiation therapy, and medical and dietary management.

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Chemodectomas (Aortic and Carotid Artery Neuroendocrine Tumors)

A chemodectoma is a type of tumor made up of chemoreceptor cells. Chemoreceptor cells detect chemical changes in the body and respond by regulating chemical or physical processes. These tumors are most often seen along one of the carotid arteries and the aorta. Brachycephalic breeds are more predisposed to these types of tumors, though they may occur in any dog breed. These tumors are usually locally aggressive, however, there are rare cases of metastasis to other organs, including the lungs, lymph nodes, and bone.

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Oral Tumors - Peripheral Odontogenic Fibromas

Odontogenic fibromas, sometimes previously referred to as an epulis, are benign tumors of the mouth often at the front of the upper jaw. These may be locally invasive and may cause some oral pain. Surgery is the recommended course of action to treat this condition.

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Oral Tumors: Papillomas and Sarcoids

This handout discusses some of the more common forms of oral tumors in pets. Highlighted are Papillomas (“Warts”) and Fibropapillomas, both of wish are caused by viral infection. Clinical signs, diagnostic methods, and treatment options are highlighted.

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Oral Tumors - Squamous Cell Carcinoma

Oral squamous cell carcinomas (SCC) are the most common oral tumor in cats, and second most common in dogs. These tumors are locally aggressive, with a possibility to metastasize. Regardless of the location of SCC, surgery is the typically the standard treatment. Radiation therapy may be recommended following surgery or as a primary treatment for palliative care. Staging is recommended for all cases. If metastasis is present chemotherapy is often pursued.

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Ovarian Tumors

Ovarian tumors are quite rare in North American pets, mainly due to routine spaying practices. This handout discusses ovarian tumors in dogs and cats. The various forms of ovarian tumors, clinical signs, diagnosis, treatment, and prognosis of this cancer are outlined.

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Pancreatic Tumors

Primary pancreatic tumors are rare in dogs and cats. Exocrine tumors include adenomas and adenocarcinomas, and endocrine tumors include insulinomas, gastrinomas, and glucagonomas. Insulinomas are the most common type of pancreatic tumor, followed by adenocarcinomas. Both tumors are more common in dogs than cats. Large breed dogs and Siamese cats may be predisposed. Insulinomas are usually diagnosed with the finding of hypoglycemia with normal to high insulin on bloodwork and concomitant clinical signs. Adenocarcinomas typically go undetected until the clinical signs of metastasis are evident. For both tumors, diagnostic imaging and exploratory surgery with tumor removal (or biopsy) and histopathology are needed for a definitive diagnosis. Insulinomas can be treated with surgery and chemotherapy. Surgery is possible with adenocarcinomas, but as the cancer is more diffuse and has usually metastasized by the time of diagnosis, the prognosis is poorer. Chemotherapy and radiation therapy are ineffective in the treatment of adenocarcinomas. Given the high rate of metastasis with these tumors, staging is recommended prior to surgery.

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Parathyroid Tumors

Parathyroid tumors are uncommon in dogs and cats. Benign adenomas occur more often than malignant tumors. Keeshonds appear to have a genetic predisposition to developing parathyroid tumors, however no breed or genetic relationship has been established in cats. Pets may exhibit signs of lethargy, little or no appetite, vomiting, and muscle twitching. Diagnosis is confirmed with PTH testing and ultrasound of the neck region after hypercalcemia is observed on bloodwork. Surgery to remove the affect gland(s) is the typical treatment, however ultrasound-guided ablation may be pursued. Careful monitoring of calcium levels post-surgery is important, as some pets may develop a transient hypocalcemia and require calcium supplementation. Prognosis is excellent, and the metastatic rate for these tumors is extremely low.

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Pituitary Tumors

Clinical signs of pituitary tumors depend on whether the tumor is functional or nonfunctional. Functional tumors can cause Cushing’s disease in dogs, and both acromegaly and insulin-resistant diabetes in cats. Nonfunctional pituitary tumors can enlarge to cause neurological signs. Diagnosis may be based on the history, bloodwork, urinalysis, and sometimes a CT scan or MRI. Medical therapy is often the treatment of choice for functional tumors. Radiation therapy is another option and is usually the primary treatment for nonfunctional tumors.

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Plasma Cell Tumors and Multiple Myeloma

Plasma cell tumors develop as a result of dysregulated production of plasma cells and are relatively uncommon in dogs and cats. Some plasma cell tumors are benign and the most common locations for these tumors are the head, feet, lips, mouth, and ears. The treatment of choice for benign plasma cell tumors is surgical removal, with little to no recurrence if completely excised. Conversely, multiple myeloma is a very malignant cancer that is usually treated with chemotherapy.

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Prostate Tumors

Tumors of the prostate are relatively uncommon in dogs and extremely rare in cats. Clinical signs include bloody urine, or straining to urinate or defecate. Metastasis to the pelvic bone and/or lumbar spine is likely. Diagnosis and treatment options are discussed. Prognosis is considered poor.

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Salivary Gland Tumors

Salivary gland tumors are rare in dogs and cats. The mandibular and parotid glands are most commonly affected. Older dogs and cats, Poodle and Spaniel breed dogs and Siamese breed cats, and male cats are at a higher risk for salivary gland tumors. The most commonly reported salivary gland tumor is the adenocarcinoma. Signs include swelling of the upper neck or ear base, halitosis, anorexia, weight loss, difficulty eating, pain, and lethargy. Fine needle aspiration may be used to differentiate between neoplastic and non-neoplastic masses. Biopsy provides a definitive diagnosis. General staging as well as CT scan or MRI are recommended since these tumors have a tendency to be locally invasive and metastasize. The treatment of choice is usually surgical excision. If complete excision is not possible, adjunct radiation therapy may be pursued.

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Basal Cell Tumors

A basal cell tumor is an abnormal growth/mass resulting from the uncontrolled division of basal cells. There is no known reason for the development of these tumors in cats and dogs; however, certain breeds of dogs and cats are more likely to develop basal cell tumors, including Wirehaired Pointing Griffons, Kerry Blue and Wheaten Terriers, Cocker Spaniels, Poodles, and Siamese Cats. Fine needle aspiration may aid to guide the diagnosis, but definitive diagnoses are typically made via surgical removal and histopathology. There are few reports of local recurrence and metastasis (spread) does not appear to occur. With adequate surgical removal, long-term control is likely.

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Cutaneous Histiocytoma in Dogs

The histiocyte group of cells are part of the body's immune surveillance system. They take up and process foreign antigens, such as pollens and viral, bacterial and fungal microorganisms.

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Lymphoid Tumors of the Skin

Lymphocytes are specialized cells that function as part of the body's immune system, and are key cells in the body's ability to fight and prevent infection. Lymphocytes are found in the blood and tissues throughout the body, and are in particular concentration in lymph nodes and other 'lymphoid tissue'.

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Melanomas of the Skin and Toes

Melanocytes are cells that produce a pigment called melanin. A melanoma is an abnormal production of these cells in a dysregulated manner that forms a nodule, mass, or other form of lesion. Melanomas of the skin may develop anywhere on the body and are not typically bothersome. Toe melanomas, however, can be much more painful and concerning for your pet's health. Melanomas are often black in color but some do not produce pigment (amelanotic melanoma). Fine needle aspiration or biopsy may be used for diagnosis. Melanomas of the skin and toes are treated surgically and radiation therapy may be discussed.

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Cutaneous or Reactive Histiocytosis

The histiocyte group of cells are part of the body's immune surveillance system. Cutaneous (reactive) histiocytosis is an uncommon condition of dogs. Cutaneous, reactive histiocytosis is an immune dysfunction, mainly of young dogs and probably due to persistent antigenic stimulation by a variety of antigens (foreign proteins).

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Squamous Cell Carcinomas in Cats

Squamous cell carcinoma (SCC) is a tumor of the cells that make up the contact or upper layer of the skin. UV light exposure has been described as a developmental factor in people and appears to be associated with the development in cats. Areas affected include the ear tips, skin, toes, or peri-ocular region. Fine needle aspiration or biopsy may be performed for diagnosis. The metastatic rate does not appear overly clear, though staging is always recommended. SCC of the toe can occur as a primary tumor or may have spread from the lung (lung-digit syndrome). Surgery is almost always recommended in any case of SCC; the role of chemotherapy is controversial. Radiation therapy has an excellent response rate in cats with the SCC affecting the nasal planum and may give long-term tumor control.

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Squamous Cell Carcinomas in Dogs

Squamous cell carcinoma (SCC) is a tumor of the cells that make up the contact or upper layer of the skin. UV light exposure has been described as a developmental factor in people, though it is still in question as to the role for dogs. Several breeds are known to be predisposed to this type of cancer. This tumor may affect any area of the skin, the nose/nasal planum, or the toes. Fine needle aspiration or biopsy may be performed for diagnosis. About 30% of dogs with the digital form of the disease will have evidence of spread. Regardless of the location, surgery is typically the treatment of choice, and staging is usually recommended prior to any surgery. The role of chemotherapy remains controversial.

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Stomach Tumors

Stomach tumors are uncommon in dogs and cats. There are many kinds, including leiomyosarcomas, lymphomas, adenocarcinomas, mast cell tumors, fibrosarcomas, plasmacytomas, gastrointestinal stromal tumors (GISTs), and carcinoids (all malignant); and leiomyomas, adenomatous polyps, and adenomas (benign). Most tumors are malignant. Stomach tumors are more prevalent in older animals, males, and certain breeds. The signs of stomach tumors include chronic vomiting, inappetence, lethargy, and weight loss. Sometimes tumor ulceration will cause anemia. Paraneoplastic syndromes are possible with the muscle tumors. Stomach tumors may be diagnosed with imaging, endoscopy, or surgery, with a biopsy. Treatment may involve surgery, chemotherapy, or radiation therapy.

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Testicular Tumors

Testicular tumors are generally not aggressive and have a low metastatic rate. Pets with undescended testicles (cryptorchid) are predisposed to the development of certain testicular tumors. Hyperestogenism is possible with Sertoli cell tumors. In any cryptorchid pet, removal of both testicles should be pursued. Intraabdominal tumors in cryptorchid pets may cause lethargy, decreased appetite, and fever. Standard staging is recommended in all cases, including a rectal exam. Surgery is typically the treatment of choice and may be combined with radiation therapy or chemotherapy if metastasis is evident.

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Thyroid Tumors

Thyroid tumors can be benign or malignant and functional or nonfunctional. In dogs, they are usually malignant and nonfunctional, whereas in cats, they are usually benign and functional. A swelling in the neck may be the only sign in a dog, however a change in bark, coughing, difficulty swallowing, facial swelling, rapid breathing, breathlessness, weight loss, and a loss of appetite are possible. In cats, the signs are related to excess thyroid hormone production (hyperthyroidism). Thyroid tumors are diagnosed with a physical examination, bloodwork, various forms of diagnostic imaging, and in dogs, a tissue biopsy. In dogs, staging is required to determine the presence of spread. A variety of treatment options are available. These include surgery, radiation, chemotherapy, and radioactive iodine therapy in dogs, and medication, radioactive iodine therapy, surgery, and dietary therapy in cats. With appropriate treatment, the prognosis for dogs and cats with thyroid tumors is good.

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Transmissible Venereal Tumor

Transmissible venereal tumors (TVTs) arise from immune cells called histiocytes. Dogs develop this tumor from direct contact with already affected dogs, most notably during sexual contact. The tumors typically develop on the penis, prepuce, vulva, and vagina, though can develop on the skin, eyes, oral, and nasal cavities as well. The tumors are usually cauliflower-like in appearance. Clinical signs are dependent on the location, but typically the tumors ulcerate and bleed. Metastasis is rare but can affect lymph nodes and other areas of the body. Treatment may include chemotherapy or radiation therapy (for those resistant to chemotherapy). Prognosis is usually good with a high response rate to chemotherapy.

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Urinary Tract Tumors

Tumors of the urinary tract may present anywhere from the kidneys to the tip of the urethra. Tumors of the bladder are most common in the dog whereas tumors involving the kidneys are more prevalent in cats. Unfortunately, many tumors of the urinary tract are malignant and treatment options may be limited. Surgery is possible in select cases. Medical treatment may be beneficial in cases where surgery is not possible.

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Uterine Tumors

Uterine tumors are quite rare in North American pets, mainly due to routine spaying practices. Several types of tumors can arise from the tissues of the uterus. This handout discusses uterine tumors in dogs and cats. The various types of these tumors, along with the clinical signs, diagnosis, treatment, and prevention of this condition are outlined.

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Vascular Tumors Affecting the Skin

Vascular tumors of the skin develop from the blood vessels of the skin. These tumors may arise anywhere on the body and appear as a firm and raised lump on or under the skin. Hemangiomas may ulcerate and bleed; hemangiosarcomas may bleed into the surrounding tissues. This type of tumor is typically diagnosed via a tissue biopsy or surgical removal of the entire tumor. Surgery is the recommended treatment for vascular tumors of the skin.

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Visceral Vascular Tumors

Visceral vascular tumors are tumors that develop from the blood vessels found in the internal organs of the body, most commonly the heart, liver, and spleen, although other locations, such as the urinary bladder, are possible. There are two forms of visceral vascular tumors: hemangiomas and hemangiosarcomas. Certain breeds, such as German Shepherds, Labrador Retrievers, and Golden Retrievers, are particularly predisposed to developing hemangiosarcoma. The clinical signs vary depending on the location of the tumor. This type of tumor is often diagnosed with ultrasound of the chest or abdomen depending on the location of the tumor. Surgery is the recommended treatment option and chemotherapy may be recommended.

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What is Cancer?

Cancer is classically described as the abnormal growth of a specific cell type with the potential to invade many parts of the body and damage organs or tissues. Cancer has many hallmarks, including its ability to evade the immune system’s safeguards, uncontrollably proliferate, and metastasize (spread). Several genetic and environmental factors have been implicated in the development of cancers, though their origin is likely multifactorial. This handout broadly describes what cancer is, what causes it, what the signs are, and how it can be diagnosed and treated.

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Tumors - Lipomas in Birds

Lipomas are benign fat tumors commonly found in Budgies, some Amazon parrots, galahs and sulphur crested cockatoos. They are most often found under the skin on the sternum (breastbone or keel bone) or on the ventral abdomen, but can be anywhere on the body.

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Tumors - Xanthomas in Birds

Xanthomas are discrete masses or diffuse, thickened areas of skin that are yellow-orange and dimpled in appearance. They are accumulations of fat and cholesterol and are most commonly found in cockatiels and budgies (and they are more often found in females).

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Hormonal Diseases in Ferrets

There are four major hormonal diseases in ferrets. This handout covers adrenal gland disease and diabetes mellitus. Adrenal gland disease occurs in a large number of ferrets in North America, while diabetes mellitus is a rare, but important problem.

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Tumors in Ferrets

Malignant lymphoma (lymphosarcoma) and leukemia are among the most common malignancies seen in ferrets. Diagnosis may be made by fine needle aspiration or biopsy. For a dedicated owner with a compliant patient, surgery and/or treatment with chemotherapy is an option. Remission of lymphoma is possible with treatment in ferrets, but recurrence is common. Ferrets also commonly develop insulin-producing tumors of the pancreas that lower the ferret’s blood sugar and cause weakness, weight loss, lethargy, seizures, coma, and death. Insulinoma commonly spreads from the pancreas to the liver, so surgical removal of pancreatic insulinoma nodules may not be curative. Affected ferrets respond well for months to years to medical therapy with glucose-promoting drugs (prednisone) and anti-insulin drugs (diazoxide). Drugs suppress effects of the tumor but do not eliminate it; and ferrets on medical treatment must have their medications increased over time as the tumor grows.

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Diseases in Rabbits

Common conditions of pet rabbits include upper respiratory tract infections, internal and external parasites, dental disease, GI stasis, uterine problems, and pododermatitis. Upper respiratory infections are often caused by bacteria including Pasteurella multocida. Rabbits can become infected with various intestinal parasites, as well as external parasites such as ear and fur mites, fleas, and occasionally ticks. Rabbits’ teeth are continuously growing but chewing food, as well as chewing on wooden blocks, branches, and toys, helps them wear their teeth down at a rate equal to their growth. Occasionally, tooth or jaw trauma or disease causes misalignment of the upper and lower jaws and overgrowth of teeth results. Regular yearly check-ups enables early diagnosis and treatment of some rabbit diseases. Whenever a rabbit stops eating, for whatever reason, it is important to take her to see your veterinarian immediately for an evaluation.

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Diseases in Rodents

Common conditions of pet rodents include respiratory diseases, gastrointestinal problems, dental problems, and tumors. Signs of respiratory disease in rodents include nasal and/or ocular discharge in mild infections, and wheezing, coughing, and open-mouth breathing in severe infections. Gastrointestinal disease, including diarrhea from various causes and gastrointestinal stasis is common in pet rodents. All rodents have teeth that grow continuously throughout their lives. Occasionally, these teeth grow too long and cut into the gums, causing pain, or prevent the mouth from closing properly, which often makes the pet stop eating. Just as in people, cancer is often seen in pet rodents, especially mammary (breast) tumors in rats and mice. Rodents with signs of respiratory or GI disease or evidence of a tumor should be seen by a veterinarian who can properly diagnose and treat the underlying condition.

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Osteosarcoma in Dogs

Osteosarcoma, or bone cancer, is common in large breed dogs and is very aggressive, with upwards of 90-95% of patients having micrometastasis. Osteosarcoma is very painful. Lameness or a distinct swelling may be noted. Amputation is by far the most common treatment with chemotherapy following surgery. Radiation therapy may also be an option.

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Ferrets - Mast Cell Tumors

Mast cell tumors are the most common skin tumor found in ferrets. They can also be found internally on the spleen. They arise from a cell type called a mast cell. In dogs and less so in cats, these tumors can vary from benign to highly malignant.

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Tumors in Birds

While not as commonly seen as they are in dogs and cats, tumors do occur in birds. Birds of any age can develop tumors.

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Keratoma in Horses

A keratoma is a rare benign tumor of the inner layer of keratin-producing epidermal hoof wall cells that forms inside a horse's foot. As the tumor slowly grows, it expands and separates the hoof wall laminae, causing pain and lameness.

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Sarcoids in Horses

Equine sarcoids are the most common tumors seen and account for approximately nine out of every ten skin tumors seen in horses. They are non-malignant (i.e., they do not spread throughout the body) but do grow larger and often spread and multiply locally.

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Lymphoma or Lymphosarcoma in Ferrets

Ferrets can suffer from tumors in any part of their body, ranging from benign cancers of the skin to aggressive malignant tumors of internal organs. The clinical signs depend on the type of tumor, the organ involved, and the stage of the disease. For a dedicated owner with an otherwise healthy-looking patient, treatment with chemotherapy is a very good option.

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Oral Tumors in Dogs - An Overview

Like humans, benign and malignant tumors occur in dogs’ mouths. Peripheral odontogenic fibromas (POF) are the most common benign tumors while oral melanomas, squamous cell carcinomas, and fibrosarcomas are the most prevalent malignant tumors in dogs. Diagnosis may be performed via fine needle aspiration or biopsy. Spread to mandibular lymph nodes does occur. Fine needle aspiration of the lymph nodes is recommended when malignant tumors are suspected. Tumor staging including laboratory testing as well as CT imaging helps to plan therapy.

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Pneumothorax in Dogs

The definition of a pneumothorax is an accumulation of air outside the lungs, but inside the chest wall. The air outside the lung prevents the lungs from inflating normally, and can lead to lung collapse. There are several variations of pneumothorax.

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Multidrug Resistance Mutation (MDR1)

Many herding breeds (most commonly Collies and Australian Shepherds) have a mutation at the MDR1 gene that makes them more sensitive to the negative effects of certain medications. These drugs include several antiparasitic agents (when given at high doses), the antidiarrheal agent loperamide (Imodium®), and several anticancer drugs. The effects of the mutation vary in severity, depending on whether the dog carries one or two copies of the mutation. There is a commercially-available test that assesses blood samples or a cheek swab for the presence of the MDR1 mutation.

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Cutaneous Lymphoma in Dogs

Systemic lymphoma is a very common cancer in dogs, but the cutaneous form is actually quite rare. Current statistics suggest that cutaneous lymphoma accounts for only about 5% of canine lymphoma cases.

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Cutaneous Lymphoma in Cats

Skin cancers are fairly common in cats, but cutaneous lymphoma is quite uncommon. Only about 3% of lymphoma cases in cats occur in the skin. There may be a linkage between feline leukemia virus (FeLV) and feline cutaneous lymphoma. Unfortunately, feline cutaneous lymphoma is considered incurable.

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Round Cell Tumors in Dogs

Round cell tumors are among the most common skin tumors in dogs, and they typically form just under the skin, although they may change the surface of the skin above them. When caught early, most round cell tumors are removed easily, and surgery is generally curative. The most important take home message is to be vigilant, and to have any skin lumps or bumps assessed by your veterinarian promptly.

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Lymphoma in Dogs

Lymphoma is a cancer of the lymph nodes and lymphatic system. This cancer may be localized to one particular region, or may spread throughout the entire body. Lymphoma is a relatively common cancer, accounting for 15-20% of new cancer diagnoses in dogs. The prognosis for lymphoma varies, depending on various characteristics that can only be determined by specialized testing.

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Infertility in Female Dogs

Infertility in a female dog is defined as the inability to conceive and deliver viable puppies, even when mated multiple times with a known fertile male surrounding the time of ovulation. This handout outlines the varying causes of infertility in female dogs and how they may be diagnosed and treated.

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Lymphoma in Cats

Lymphoma is a cancer of the lymphocytes. Lymphocytes are cells that are involved in the immune system. Feline lymphoma most commonly affects the intestines; therefore, clinical signs of lymphoma are often similar to other intestinal diseases. Diagnosing lymphoma requires finding cancerous cells on microscopic examination. This cancer cannot be prevented, but the likelihood of a cat developing lymphoma can be decreased by preventing feline leukemia virus infection.

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Sweat Gland, Hair Follicle, and Sebaceous Gland Tumors

Skin gland, hair follicle, and sebaceous gland tumors are often benign. Matrical carcinoma and sebaceous gland adenocarcinoma are rare and more aggressive forms of the disease. Regardless of the type (sweat, hair, or sebaceous) diagnosis is made by fine needle aspiration, biopsy, and/or surgical removal and histopathology. Further treatment is reviewed.

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Radiation Therapy

Radiation is a type of energy produced naturally by the sun, earth, and rocks and artificially by machines. Although several types of tumors can be treated with radiation therapy alone (e.g., nasal tumors, brain tumors, and certain types of lymphoma), radiation therapy is most commonly used to destroy or limit the growth of cancer cells left behind (i.e., microscopic disease) after a tumor has been surgically removed. Side effects depend on the type and location of the tumor and its surrounding tissues.

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Chemotherapy

Chemotherapy is the therapeutic use of chemical agents to destroy, or inhibit the growth and division of cancer cells. Chemotherapy is usually used when tumors are widespread or when there is significant or immediate risk of spread from the primary location. It is often used following the surgical removal of tumors. In some cases, chemotherapy is started prior to surgery. Different protocols are used depending on the drug and the type of cancer being treated. The side effects of chemotherapy are related to the effects of chemotherapy on normal – as well as cancerous – cells. The principal goal with cancer care in pets is to provide cancer control without reducing quality of life. With pets, chemotherapy protocols are purposefully designed so the treatment does not become worse than the disease.

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Chondrosarcoma in Dogs

Chondrosarcomas arise from cartilage, which is a connective tissue primarily found where bones meet with joints, as well as at other locations in the body (such as the nasal cavity, ribs, etc.). Chondrosarcoma is the second most common primary bone tumor in dogs. Canine chondrosarcoma most commonly affects the flat bones of the body, such as the ribs, skull, nasal cavity and pelvis, although the limbs can also be affected. Aggressive surgical resection is typically recommended, although radiation therapy may also be used (depending on location). Metastasis may occur, but is relatively uncommon.

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Chondrosarcoma in Dogs

Chondrosarcomas arise from cartilage, which is a connective tissue primarily found where bones meet with joints, as well as at other locations in the body (such as the nasal cavity, ribs, etc.). Chondrosarcoma is the second most common primary bone tumor in dogs. Canine chondrosarcoma most commonly affects the flat bones of the body, such as the ribs, skull, nasal cavity and pelvis, although the limbs can also be affected. Aggressive surgical resection is typically recommended, although radiation therapy may also be used (depending on location). Metastasis may occur, but is relatively uncommon.

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Chondrosarcoma in Dogs

Chondrosarcomas arise from cartilage, which is a connective tissue primarily found where bones meet with joints, as well as at other locations in the body (such as the nasal cavity, ribs, etc.). Chondrosarcoma is the second most common primary bone tumor in dogs. Canine chondrosarcoma most commonly affects the flat bones of the body, such as the ribs, skull, nasal cavity and pelvis, although the limbs can also be affected. Aggressive surgical resection is typically recommended, although radiation therapy may also be used (depending on location). Metastasis may occur, but is relatively uncommon.

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Chondrosarcoma in Cats

Chondrosarcomas arise from cartilage, which is a connective tissue primarily found where bones meet with joints, as well as at other locations in the body (such as the nasal cavity, ribs, etc.). Chondrosarcoma is a rare tumor in cats, but it can occur. The reason why a particular pet may develop this, or any tumor or cancer, is not straightforward. Clinical signs of chondrosarcoma may vary significantly, depending upon where the tumor arises. Although the mass may grow rapidly, less than 20% of feline chondrosarcoma cases metastasize to other parts of the body. Therefore, surgical removal is curative in many cases.

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Chondrosarcoma in Cats

Chondrosarcomas arise from cartilage, which is a connective tissue primarily found where bones meet with joints, as well as at other locations in the body (such as the nasal cavity, ribs, etc.). Chondrosarcoma is a rare tumor in cats, but it can occur. The reason why a particular pet may develop this, or any tumor or cancer, is not straightforward. Clinical signs of chondrosarcoma may vary significantly, depending upon where the tumor arises. Although the mass may grow rapidly, less than 20% of feline chondrosarcoma cases metastasize to other parts of the body. Therefore, surgical removal is curative in many cases.

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Chondrosarcoma in Cats

Chondrosarcomas arise from cartilage, which is a connective tissue primarily found where bones meet with joints, as well as at other locations in the body (such as the nasal cavity, ribs, etc.). Chondrosarcoma is a rare tumor in cats, but it can occur. The reason why a particular pet may develop this, or any tumor or cancer, is not straightforward. Clinical signs of chondrosarcoma may vary significantly, depending upon where the tumor arises. Although the mass may grow rapidly, less than 20% of feline chondrosarcoma cases metastasize to other parts of the body. Therefore, surgical removal is curative in many cases.

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Esophageal Tumors

Esophageal tumors are extremely rare in dogs and cats. There are many kinds, including squamous cell carcinomas, leiomyosarcomas, fibrosarcomas, osteosarcomas, and undifferentiated sarcomas (all malignant); and leiomyomas and plasmacytomas (benign). Most tumors are malignant. These tumors occur mostly in the upper esophagus in cats and the lower esophagus in dogs. In dogs, most cases of esophageal sarcoma are associated with spirocercosis. Esophageal cancer causes progressive signs of regurgitation, difficulty swallowing, excessive salivation, weight loss, and lack of appetite. It is diagnosed with imaging, endoscopic or surgical biopsy, and histopathology. Surgery is a treatment option, with the possibility of radiation therapy for tumors of the upper esophagus. Avermectins may be used with benign spirocercosis. Palliative care may be possible with the placement of a feeding tube.

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Intestinal Tumors

Intestinal tumors are uncommon in dogs and cats. There are many kinds, including leiomyosarcomas, lymphomas, adenocarcinomas, mast cell tumors, GISTs, plasmacytomas, carcinoids, and osteosarcomas (all malignant) and leiomyomas, adenomatous polyps, and adenomas (all benign). Most intestinal tumors are malignant. Intestinal tumors are more prevalent in older animals, males, and certain breeds. The signs of intestinal tumors vary according to the area of the intestinal tract that is affected, and can include vomiting, lack of appetite, lethargy and weight loss for the upper bowel and difficulty defecating, ribbon-like stools, and rectal prolapse with the lower bowel. Sometimes tumor ulceration causes anemia. Paraneoplastic syndromes are possible with the muscle tumors. Intestinal tumors may be diagnosed with imaging, endoscopy, or surgery, with a biopsy. Treatment may involve surgery, chemotherapy, or radiation therapy.

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AskVCA: Should I Have This Bump Checked Out On My Dog?

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