Fibroadenomatosis (fibroadenomatoid mastopathy): a benign breast lesion with composite pathologic features.

A benign breast lesion with the composite histologic features of a fibroadenoma and fibrocystic changes has been referred to previously as fibroadenomatosis or fibroadenomatoid mastopathy; this lesion is distinct from the typical well circumscribed fibroadenoma that may have fibrocystic changes. The purpose of our study was to ascertain the frequency of this change among 200 consecutive breast biopsies and excisions with a coded pathologic diagnosis of fibroadenoma and/or "fibrocystic disease"; we identified these changes in 23 (11.5%) specimens. The lesion was characterized by microscopic fibroadenomatoid foci intermingled with dilated ducts, epitheliosis, and adenosis. It is suggested that fibroadenomatosis is yet another pattern in the complex morphologic spectrum known as benign proliferative breast disease. From our experience, this particular lesion was often appreciated as a unique finding, but the appropriate diagnostic designation was in question. The natural history of fibroadenomatosis is essentially unknown. It may represent a morphologic stage in the development of fibroadenoma(s).