Canine Tumors and Cancers
University of Missouri-Columbia Scott Endowed Program in Veterinary Oncology

The most common forms of cancer are breast, skin, bone, connective tissue, oral, and lymphoma. While some cancer, such as breast cancer, is largely preventable with early spaying, the cause of most cancers is not known and therefore prevention is difficult. Bone tumors are commonly seen in the leg bones, near joints, persistent lameness and swelling of the leg an early sign of disease. Testicular tumors are seen in dogs with retained testes, but are often curable with surgery. Tumors inside the abdomen are common but it can be difficult to make an early diagnosis. Weight loss and abdominal enlargement are common signs of these tumors. With cancer of the mouth, a mass on the gums, bleeding, odor, or difficulty eating are the signs to watch for. Cancer may also develop inside the nosebleeding from the nose, difficulty breathing, or facial swelling possibly occurring. Lymphoma is characterized by one or many lymph nodes in the body becoming enlarged.

Osteosarcoma: This is the most common bone tumor in dogs. Approximately 8-10,000 dogs are diagnosed with OSA each year. Affected dogs are most commonly large or giant breed dogs and slightly more are male. The most common sites are near the wrist and shoulder, as well as near the joints in the hind leg. This cancer metastasizes frequently as 90% of patients have micrometastasis (spread of small tumors that we cannot yet see on x-rays/radiographs) at the time of diagnosis. The treatment of choice is amputation, although there are both medical and surgical options for limb sparing depending on what bone is affected. This tumor can also occur in the head and torso, in non-bone tissues, and in cats. In addition to surgery, because of the likelihood of early spread of disease (metastasis), chemotherapy is very important for complete care. With treatment of the affected leg plus chemotherapy, one year survival rates are around 60%. At the University of Missouri-Columbia Veterinary Medical Teaching Hospital, they offer novel limb salvage with Samarium which is a bone-seeking radionuclide, intended primarily to relieve the pain associated with bone cancer.

Lymphoma: Lymphoma is a common cancer of dogs and cats that can occur anywhere in the body. Lymphoma is the same as lymphosarcoma, as there is no benign variant of the disease. In dogs, it is most commonly seen in the lymph nodes. Chemotherapy is typically well tolerated and when patients are in remission, most pets enjoy a normal or near normal quality of life. Common sites for lymph nodes are under the jaw, in front of the shoulder, in the armpit, in the groin, and behind the knee.

Soft tissue sarcomas: These are tumors that originate from the cells that hold our ‘parts’ together. They have a variety of different names but behave in a similar manner. Some common tumors in this group include fibrosarcoma, peripheral nerve sheath tumor, and hemangiopericytoma. These tumors are typically aggressive locally but less likely to spread throughout the body. They are treated initially with surgery and when additional therapy is needed, are well controlled with radiation therapy.

Mast cell tumors: These are common skin tumors found in both dogs and cats. Their behavior depends on how they look under the microscope. Some tumors stay where they grow but others can spread to other parts of the body. A biopsy is required to determine the best treatment for a cat or dog but surgery is usually the first step. If additional local control is needed, radiation and/or chemotherapy may be recommended, and if a tumor is high grade and likely to spread systemically, then chemotherapy will be recommended with or without radiation. Newer chemotherapy protocols have given more favorable outcomes than what was reported in the past and local control is excellent with surgery and, if needed, radiation therapy.

Nasal tumors: Dogs and cats can both get tumors up inside the nasal cavity. Clinical signs include persistent discharge from the nose on one side, often with blood. Sometimes nosebleeds are seen. The treatment of choice for nasal tumors is radiation therapy alone. Surgery does not seem to improve survival and may cause more discharge, but may be used in select cases. Chemotherapy has been tried in a few cases but is not as effective as radiation. These tumors can metastasize but more often the tumor in the nose is the main problem for the pet. Average survival with radiation therapy is 1-1 yrs, with no treatment, depending on the clinical signs a dog is experiencing, survival is usually less than 6 months.

Hemangiosarcoma: This is an aggressive cancer that occurs most often in the spleen of dogs. It has also been seen in the heart and skin of dogs. It is a tumor of the blood vessels and since there are blood vessels in every tissue, this tumor can be seen anywhere in the body. This cancer is highly metastatic and the treatment of choice is removal of the spleen followed by chemotherapy. Based on currently available published information, the average survival following surgery alone is around 2 months and with the addition of chemotherapy is around 6 months. The exception is with skin lesions which have a much lower metastatic rate and much longer survival rate.

The following links provide more comprehensive information on types of canine tumors and cancers. 
Anal Sac Gland Tumors  
Apocrine Gland Tumors  
Basal Cell Tumor  
Basosquamous Carcinoma
Benign Melanocytic Tumors  
Bone Tumors
Ceruminous Gland Tumors
Chondrosarcoma (Larynx and Trachea)
Chondrosarcoma (Nasal and Paranasal Sinus)
Ear Tumors
Fibrosarcoma (Bone)
Fibrosarcoma (Nasal and Paranasal Sinus)
Gastrointestinal Neoplasia
Hepatic Neoplasia (Liver Tumors)
Hepatoid Gland Tumors  
Hemangiopericytoma (includes spindle cell sarcomas)
Lymphoma/Lymphosarcoma: Relationship to
Malignant Fibrous Histiocytoma
Mammary Gland Tumors
Mast Cell Tumors
Meibomian Tumors  
Nasal Passages Tumors
Papilloma (Papillomatosis) Prostatic Tumors 
Primary Lung Tumors (Pulmonary Neoplasia) 
Renal (Kidney) Neoplasia
Sebaceous Gland Tumors  
Skin Cancer
Squamous Cell Carcinoma
Splenic Masses
Subungual Squamous Cell Carcinoma
Testicular Tumors
Transitional Cell Carcinoma
Transmissible Venereal Tumor
Tumors with Differentiation to Hair Follicular Structures     
Undifferentiated Sarcoma
Urethral Prolapse and Neoplasia 
Urinary Bladder Cancer
Uterine Tumors in Dogs 
World Health Organization Histological Classification of Tumors


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