Fast Growing Tumors in Dogs

Updated February 21, 2017

Mast cell tumours (MCTs) are fast growing tumours found in dogs. They appear as raised hard lumps underneath the dog's skin. MCTs are a form of skin cancer. These tumours generally don't spread to other organs, although when it infects the lymph nodes the outcome is often fatal. MCTs are diagnosed in grades and stages based on the number of cell divisions and degree of spreading. Tumours of higher grades and stages (fast growing) unfortunately are given the worst prognosis.

Mast Cells

Mast cells are found in a dog's body. They release enzymes when stimulated by the immune system to ward off infection and irritants. When abnormal mast cells release too many enzymes, it creates a toxic reaction that results in a tumour as well as other problems, such as gastric ulcers, internal bleeding and an allergic manifestation.


The Bernese Mountain Dog Club of America reports 25 per cent of canine skin tumours are MCTs. About 50 per cent are malignant (fast growing). Most are found on the skin in the dog's legs or face, but they also can be found in the dog's spleen, liver and bone marrow.


According to Kate Connick's Courteous Canines, LLC---a canine information website---little is known about the cause of MCTs in canines. Although MCTs are more prevalent in older dogs, tumours don't discriminate and can affect dogs of various ages, gender and breed. Connick claims the average age of dogs with MCTs is eight or nine years old.


A dog owner usually is the first person to spot the tumour when he pets the dog and detects a lump on its body, prompting a visit to the veterinarian. The veterinarian takes a biopsy of the lump or removes it entirely and sends it a lab for analysis. A blood test also may be done to check for an elevated white count---an indication of a more serious infection. The lab analysis provides a grade and stage of the tumour.


Regrettably, the prognosis for a dog diagnosed with a fast growing tumour is terminal. Depending on the exact grade and stage of the cancer, tumours may be surgically removed to prolong the dog's life. Additional tissue is usually removed from around the tumour to ensure abnormal cells are eradicated. In certain cases, the dog's entire limb may be removed.
The dog is usually given drug therapy of prednisone and/or chemotherapy to reduce the tumour size and prevent rapid mastication. The dog is given pain medication to keep it comfortable and to maintain the best quality of life possible in his final weeks or months.

Cite this Article A tool to create a citation to reference this article Cite this Article

About the Author

Christie Gross has been writing since 1998. Her work writing public policy platforms for elected officials nationwide has been featured in national and local newspapers under various client pen names. Gross has a Bachelor of Arts in English and political science, as well as a Master of Public Administration from the University of Delaware.