Which statement accurately reflects the prevalence order of canine oral tumors?

• A. Lymphoma is most common, followed by melanoma.
• B. Osteosarcoma is most common, followed by squamous cell carcinoma.
• C. Melanoma is most common, followed by squamous cell carcinoma.
• D. Fibrosarcoma is most common, followed by melanoma.

Answer: (C)

The main idea here is the relative frequency of tumors that occur in a dog’s mouth. In dogs, malignant melanoma is reported as the most common oral tumor. It arises from pigment-producing cells in the oral mucosa and can show up as a pigmented or nonpigmented mass on the gums, palate, or lips. Squamous cell carcinoma is the second most common oral tumor, coming from the lining of the oral cavity and also tending toward aggressive local invasion. The other types, like fibrosarcoma or osteosarcoma, occur less frequently in the mouth than these two, so the sequence melanoma then squamous cell carcinoma best matches what veterinarians typically see in practice.