Fine Needle Aspiration Cytology of a Pilomatrixoma Misdiagnosed as Carcinoma: A Case Report

Jung, Ji Han; Kim, Young Shin; Lee, Kyo Young; Kang, Chang Suk; Shim, Sang In

Abstract

Sometimes a pilomatrixoma on upper neck can be misdiagnosed as primary salivary gland tumor, skin adnexal tumor or metastatic carcinoma. On fine needle aspiration cytology(FNAC), characteristic features are ghost cells, basaloid cells, and calcium deposits, among which presence of ghost cells seems to be the key to recognize it. Here we present a cytologically misdiagnosed case of pilomatrixoma. A 32-year-old man presented a subcutaneous mass on the right posterior neck. It has grown slowly for 1 year, and was nontender, well circumscribed, hard, and movable mass. An initial FNAC yielded only monomorphic population of highly mitotic basaloid cells, without anucleated ghost cells, chronic inflammatory cells or foreign-body giant cells, suggestive of a poorly differentiated carcinoma. However, that was inconsistent with patient's clinical findings. For further correct diagnosis, FNAC was repeated, which yielded the basaloid cells and foreign-body giant cells. The diagnosis of pilomatrixoma could be made and the mass was excised. This case demonstrates that the pilomatrixoma should be considered in the differential diagnosis of subcutaneous aspirates containing not ghost cells but a dominant population of basaloid cells.