Fine‐needle aspiration cytological findings in three cases of metastatic amelanotic melanoma to the parotid gland with divergent differentiation

This report presents the clinical and pathologic findings of three cases of metastatic amelanotic melanoma to the parotid gland. Two of the patients had a primary cutaneous tumor. Fine-needle aspiration of the parotid showed clusters of epithelioid cells and/or spindle-shaped cells with vesicular nuclei, macronucleoli, and abundant eosinophilic cytoplasm. In addition, one had striking balloon-cell features. In the immunohistochemical study, the tumors expressed S-100, HMB-45 antigen, Melan-A, and SOX10, and focally smooth-muscle actin, cytokeratin, CD56, p63, and synaptophysin. The diagnosis was challenging because the tumors were clinically thought to be primary parotid lesion and showed unusual immunohistochemical labeling for SMA, cytokeratins, p63, and neuroendocrine markers. Furthermore, the long clinical history in two of the cases made the diagnosis of a metastatic lesion less likely. Diagnostic errors can be reduced by integrating cytomorphologic, histologic, immunohistochemical, and clinical findings.

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