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.