Last winter, Martina Navratilova announced she had been diagnosed with both breast cancer and throat cancer. Unfortunately, the simultaneous occurrence of two different types of cancers in a person is not a rare occurrence, with 2% to 17% percent of people with cancer developing multiple types.

The same situation occurs in both dogs and cats, and I have detailed some specific patients in prior blogposts. In this blogpost, I’ll expand on the occurrence of more than one cancer at a time in veterinary patients.

Common Tumors Occur Commonly

I remind myself of this phrase daily. It helps me focus on determining the most likely diagnosis in my patients. The phrase also sums up pets with more than one tumor. In dogs, approximately 3% of dogs with cancer will have multiple tumors at the same time. Not so different than the human condition. Tumors most commonly occurring with a second tumor type include mast cell tumors, melanomas and thyroid tumors. Mast cell tumors are the most common malignant skin tumor of dogs and melanoma is the most common oral tumor of dogs – further confirmation that common tumors occur commonly.

Genetics May Play a Role

One of my current patients exemplifies this case. Lily is a Labrador retriever. Labs are on the list of dogs that commonly get mast cell tumors. Labs may also be at higher risk for soft tissue sarcomas. Lily had both. Now she has osteosarcoma, or bone cancer, another tumor type Labradors seem to be predisposed to getting. Despite the fact that all three of her cancers are known to occur in Labradors, scientists have not yet determined definitively if Labradors are genetically predisposed or just simply have bad luck.

Most Cancer is Bad Luck

I am not sure this phrase is comforting to those whose pets are suffering from cancer. But the fact that cancer is mostly a random event means pet owners should bear no remorse if their pet receives this devasting diagnosis.

Regarding our feline friends, I could not find any information on the prevalence of multiple synchronous tumors in cats. This is not necessarily a surprise since cats are medically underserved and have less scientific research underlying their medical care. My clinical experience tells me synchronous tumors happen in cats. We at AMC’s Cancer Institute are currently working to describe a number of cats with concurrent intestinal lymphoma and intestinal mast cell tumors.

The development of these two tumors in the same cat is likely a random event just like the double cancer diagnosis of Martina Navratilova. Fingers crossed for a good outcome for any patient with a double cancer diagnosis.