28 Jul Melanoma and ICC
Aspirates from malignant melanomas can have a varied cytologic appearance, ranging from a round cell appearance to clusters of cells suggestive of epithelial origin to individual, fusiform-shaped
EVP recently received aspirates from an oral tumor and regional lymph node from a 9-year-old, neutered male, Golden Retriever. Figure 1 is from the oral tumor. Notice how cohesive the cells are (suggestive of epithelial origin) and the lack of melanin granules. Figure 2 is from the mandibular lymph node. Metastatic disease is evident, but the cells are individualized and fusiform-shaped, suggestive of a sarcoma.
Differentials included an amelanotic melanoma and a poorly differentiated carcinoma. Immunocytochemistry (ICC) for both Melan-A and a cytokeratin was performed to further characterize the cells. The neoplastic cells were positive for Melan-A (Figure 3), but negative for cytokeratin, permitting a definitive diagnosis of malignant melanoma to be given.
EVP has recently expanded our ICC offerings to include markers for epithelial, melanocytic and mesenchymal cells, in addition to stains for B- and T- cell lymphocytes, and histiocytes.