Cytodiagnosis of epithelioid malignant melanoma (amelanotic) and diagnostic dilemmas

Abstract

Melanoma is an aggressive neoplasm, and early diagnosis can reduce mortality in such patients. Diagnosis may be delayed in amelanotic tumors. We present one such case, a 35-year-old lady with a rapidly growing mass over the right angle of mandible. Fine-needle aspiration cytology was done, and smears showed discretely arranged large epithelioid cells with high N:C ratio, prominent single to multiple nucleoli. Occasional binucleated and multinucleated tumor giant cells were also noted. Poorly differentiated carcinoma, high-grade non-Hodgkin lymphoma, amelanotic melanoma, and pleomorphic sarcoma were included as differential diagnoses. Immunocytochemistry (ICC) revealed Melan-A/MART-1 positivity in some cells and S-100 positivity in most tumor cells. Desmin, pancytokeratin, and leukocyte common antigen were negative. Based on cytomorphological features and ICC findings, a diagnosis of epithelioid variant of amelanotic melanoma was rendered. Later on, true cut biopsy and histologic examination of excised specimen and adjunct immunohistochemistry with positive Melan-A and S-100 confirmed the diagnosis.