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Educational Articles

Dogs + Cancer & Tumors

  • 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.

  • Intestinal tumors are uncommon in dogs and cats, comprising about 2% of all cancers. There are many kinds, including leiomyosarcomas, lymphomas, adenocarcinomas, mast cell tumors, gastrointestinal stromal 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 and certain breeds. Signs, diagnosis, and treatment are discussed.

  • 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.

  • Lung tumors are considered rare in cats and dogs. Many pets may not show symptoms at first, and a tumor may be found coincidentally. Depending on the type and stage of cancer, treatment may be possible; otherwise, symptomatic supportive care may be an alternative option.

  • 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 or cavity effusions because of lymphatic obstruction and leakage. 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.

  • 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.

  • 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.

  • 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.

  • Mast cell tumors are most common in the skin of dogs and may appear red, ulcerated, or swollen. They can be itchy and can fluctuate in size. Tumors can range from lower-grade, with minimal spread, to higher-grade, with a high risk of local invasion. Treatment usually involves surgical removal and may require supportive treatment including chemotherapy, radiation therapy, and therapy to target the mutation that instigated the tumor.

  • Melanomas are cancerous growths of the cells responsible for pigmentation of the skin. They can develop anywhere on the body but those on the toes carry the highest chance for malignancy. They may be painful and you may notice your pet licking at the affected area. Surgery is often the treatment of choice and may be followed up with radiation or chemotherapy.