Clinical Rounds: Battling a Labrador's oral malignant melanoma - Veterinary Medicine
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Clinical Rounds: Battling a Labrador's oral malignant melanoma
After a referring veterinarian diagnosed this deadly neoplasm in a senior Labrador retriever, this team of experts stepped in to help extend the dog's life with targeted treatment. What can you learn from their approach to help your patients?



Julia Lankton, DVM, DACVP

Julia Lankton, DVM, DACVP
Canine oral malignant melanoma most commonly appears on the gingiva or lips and less often on the cheek, tongue, or palate.10 The degree of melanin pigmentation varies, and tumors can range from heavily pigmented to amelanotic.

In addition to cytoplasmic pigmentation, characteristic histologic features include junctional activity (clusters of neoplastic cells at the mucosal-submucosal junction) and nests of neoplastic cells within the mid- to upper epithelium.

2. The histologic appearance of the tumor in this case. The neoplasm is composed of sheets of pleomorphic cells with a vesicular nucleus, a prominent nucleolus, and a variable amount of cytoplasmic melanin.
Poorly differentiated melanomas can present a diagnostic challenge to pathologists, and immunohistochemistry may be recommended to confirm the cell of origin. Melan-A is the most specific immunohistochemical marker and is also highly sensitive. Neoplastic cells are also typically positive for vimentin, S100, and neuron-specific enolase. Although most canine oral melanomas exhibit aggressive biological behavior, a subset of histologically well differentiated tumors have a prolonged clinical course (Figure 2).11


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