Educational Articles

Dogs + Tumors

  • Radiation therapy is the medical use of high dose radiation to destroy cancer cells by damaging the cells’ DNA to interfere with cell replication and kill them. It may be used on its own or in combination with other treatments, such as surgery or chemotherapy, or to reduce the size of very large tumors prior to surgery. There are several radiation protocols used in veterinary medicine. Your veterinary oncologist will choose the therapy most appropriate for your pet’s individual situation.

  • 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.

  • 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.

  • Seizures and syncope are commonly confused with one another due to similarities in the appearance of these episodes. Both present with collapse but there are several details, explained in this handout, that can differentiate between them, which is important for determining treatment. The prognosis for each condition varies depending on the underlying causes.

  • 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.

  • Squamous cell carcinoma 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. 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.

  • 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.

  • Skin gland, hair follicle, and sebaceous gland tumors are more commonly found to be benign. Matrical carcionoma 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 initial surgical removal and histopathology. In the majority of cases, surgery is recommended and other treatments are unnecessary. Chemotherapy and/or radiation therapy in pets with matrical carcinomas or sebaceous gland adenocarcinomas may be recommended.

  • The three most common testicular tumors are seminomas, Sertoli cell tumors, and interstitial cell tumors. Though other tumor types are possible, testicular tumors as a whole are generally not aggressive and have a low metastatic rate. Pets that are cryptorchid are predisposed to the development of Sertoli cell tumors and seminomas. 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.

  • 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.