[Infiltrating lobular carcinoma of the breast with histiocytoid features: three cases]

Histiocytoid carcinoma of the breast, a cellular variant of invasive breast cancer, is mainly found among infiltrating lobular carcinomas (ILC). It can be easily confused with benign conditions or other mammary tumors also composed of cells with a pink granular to foamy cytoplasm and an eccentric nucleus. We report 3 cases of histiocytoid ILC. Our aim is to discuss recent immunocytochemical data that could suggest a special type of apocrine differentiation of tumor cells, including a diffuse immunoreactivity for GCDFP-15 (Gross Cystic Disease Fluid Protein 15) and a predominant expression of androgen receptor, and to describe the features useful for the differential diagnosis.