Fine needle aspiration cytology of argyrophilic mucinous carcinoma of the male breast

The results of fine needle aspiration (FNA) cytology of a case of argyrophilic mucinous carcinoma of the male breast is presented. The smear obtained from the tumor showed many loose clusters of atypical cells with abundant granular cytoplasm in the mucous background. Most tumor cells showed a plasmacytoid appearance with eccentric nuclei. Numerous fine granules and a few large droplets were found in the cytoplasm. The characteristic light microscopic feature of this lesion was organoid nest formation of tumor cells in mucous lakes. The Grimelius method revealed numerous argyrophilic granules in the cytoplasm and immunohistochemistry showed a positive reaction for chromogranin A. Thus, this tumor revealed the cytomor-phologic characteristics of mucinous as well as argyrophilic carcinoma, simultaneously.