A Rare Melanoma Variant: Small Cell Malignant Melanoma Metastasis in the Lymph Node.

Small cell malignant melanoma (SCMM) is a rare melanoma variant, and its prognosis is worse than other melanomas. A case of SCMM metastasis on the mediastinal lymph node is presented in this study. A 54-year-old male patient had a lesion on the palmar side of the right hand and mediastinal lymph node metastasis. Fine needle aspiration biopsies were performed from the lymph nodes. Cytologically, cellular smears consisted of isolated discohesive cells, nuclear aggregates, small layers of cells, and pseudo-rosettes. Two kinds of cells were observed: one with small, round-oval cells, and the other with small to medium cells. Immunohistochemically, tumor cells were positive with S-100, SRY-related HMG-box gene 10, MelanA, and human melanoma black 45. Friend leukemia virus integration 1 was positive in over 10% of tumor cells. Metastatic malignant melanoma may present with different cytomorphologic features. SCMM is a tumor to be aware of because it can be confused with other small round blue cells and misdiagnosed.