Papillary formations in metastatic melanoma

Cytomorphologic features of melanoma can be extremely variable, in that the y can mimic other poorly differentiated neoplasms. Ten cases of metastatic melanoma with distinct, cohesive, papillary tissue fragments observed in fi ne-needle aspiration (FNA) specimens are reported. These papillary fragment s exhibited a central fibrovascular core with attached tumor cells. in a ba ckground of single scattered malignant cells, macrophages, and focal necros is. The aspiration sites included regional or distant palpable lymph nodes, pancreas, bone, and skin. Nine cases had a histologic diagnosis of primary cutaneous melanoma, and in one case the primary skin tumor was detected af ter the diagnosis ic as established by FNA of the metastasis. Immunohistoch emical studies (S-100 protein, HMB-45 antigen, and factor VIII) were perfor med in four cases, and electron microscopy in one. confirming the diagnosis of melanoma. Art awareness of this cytomorphologic variation of papillary formations in cytology preparations from metastatic melanoma is important a nd can prevent potential inaccurate interpretation. (C) Wiley-Liss, Inc.