Background: Extramedullary plasmacytoma (EMP) of the breast is extremely rare, especially that not associated with multiple myeloma.

Methods: A case of plasmacytoma of the breast in a 73-year-old man was diagnosed by fine needle aspiration cytology (FNAC). Aspiration smears revealed a dispersed population of plasmacytoid cells at various stages of maturation. The tumor was excised, and the histologic sections confirmed the cytologic diagnosis.

Conclusions: FNAC diagnosis of plasmacytoma of the breast offers the opportunity to distinguish these neoplasms from primary mammary tumors and avoid unnecessary surgery.