Fine-needle aspiration cytology of a mammary myofibroblastoma: A case report on the role of immunohistochemistry and cell block preparations and a review of the literature.

Myofibroblastoma (MFB) is a benign tumor of the mammary stroma with predominant myofibroblastic differention. The cytologic reports of MFB are very few in the available literature. From the cytodiagnostic point of view about 21 cases of MFB with cytological evaluation by fine-needle aspiration cytology (FNAC) have been encountered in the English-language literature: A 35-year-old woman presented with lump in the left breast. FNAC showed mild degree of pleomorphism with occasional groups with fibrous stroma and tumoral cells. A few benign epithelial cell groups were seen. Hematoxylin-eosin-stained sections of cell block preparation from the aspirate showed fascicles of spindle cells forming whorl structures. Three months later, excision biopsy was performed. The diagnosis was a classic variant of MFB. On immunohistochemical examination, sections were found to be highly positive for vimentin, CD34, and bcl- 2. In light of these findings, cell block material was retrospectively reviewed both morphologically and immunhistochemically. The findings of resection and cell block material were found to be very similar. MFB may cause a potential diagnostic pitfall while interpreting FNAC due to its wide differential diagnosis spectrum. We concluded that cytology and cell block findings complement each other. Diagn. Cytopathol. 2016;44:1064-1069. © 2016 Wiley Periodicals, Inc.