Benign granular cell tumor of the breast: a misleading disease.

Granular cell tumor (GCT) is a relatively rare neoplasm, and almost always benign in its prognostic behavior. Location of this tumor in the breast presents serious problems for differential diagnosis, both from a clinical point of view and at gross pathological examination, because of its resemblance to carcinoma. Fine needle aspiration biopsy and intraoperative frozen section examination may not be of any further help. The histogenesis of these lesions has been widely debated in the past, but no universally accepted conclusion has been reached. Most GCTs appear to be derived from Schwann cells, but many different neoplastic and non-neoplastic lesions show granular cell changes. Therefore, GCT should not be considered as a single entity but as the result of a cytoplasmic change due to still unknown metabolic alterations that may occur in various cell types. No firm conclusions can be drawn regarding the suspected hormonal influence on the development of breast GCT. The authors describe three typical cases of breast GCT that occurred in patients of different ages, and discuss the most important questions concerning this lesion.