Histiocytoid change in breast carcinoma: a report of 3 cases with an unusual cytomorphologic pattern of apocrine change.

BACKGROUND: Breast carcinomas composed predominantly or exclusively of cells with foamy and/or granular cytoplasm have been termed histiocytoid breast carcinoma. CASES: Three cases of HBC had fine needle aspirates that were moderately cellular and composed of cells with abundant foamy and/or granular cytoplasm, arranged in loosely cohesive groups and dispersed singly. The cells showed subtle cytologic atypia, including nuclear hyperchromasia and slightly irregular nuclear outlines. Definitive cytologic diagnosis was not possible in the 3 cases, and they were reported as "suspicious for malignancy." Core biopsies of 2 cases showed a typical Indian file pattern of invasive lobular carcinoma, while the third case was composed of sheets of discohesive histiocytoid cells admixed with a prominent lymphoid infiltrate. All 3 cases were E-cadherin negative, confirming their lobular nature.
CONCLUSION: HBC represents an unusual morphologic pattern of apocrine change that may be seen in lobular and ductal breast carcinomas. Recognition of these lesions is vital in that they may be mistaken for a variety of other entities composed of foamy/granular cells; some of those entities have vastly different implications for treatment and prognosis.