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Tumors

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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 an important problem.

  • An insulinoma is a tumor that involves the beta cells of the pancreas. Beta cells are the cells that produce the hormone insulin. Insulinomas are surprisingly common in ferrets.

  • 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.

  • 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.