Sinonasal malignant melanoma with metastasis: Immunohistochemistry meeting the diagnostic challenge.

Sinonasal malignant melanoma is one of the uncommon and highly aggressive tumors of the sinonasal cavity. Cytomorphological features in a metastatic lymph node may reveal a diagnosis of malignant melanoma. This case had nondiagnostic cytological and histopathological features, which could suggest malignant melanoma. Immunohistochemistry in such cases becomes the primary method for establishing the diagnosis of malignant melanoma at an uncommon site.