Melanoma and ICC

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 cells that are non-specific for mesenchymal cell origin.  All three appearances may be present in aspirates from the same tumor.  Making a definitive diagnosis of melanoma can be difficult if cells lack cytoplasmic melanin granules.   

Figure 1

Figure 2

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.

Figure 3

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.