Histopathology of fibroadenoma of the breast

The aim of this study was to make a thorough inventory of the histologic fe atures of epithelium and stroma within the adjacent to breast fibroadenomas in 396 cases. Brest fibroadenomas seemed to display a wide spectrum of pro liferative and nonproliferative histologic changes. Hyperplasia (excluding mild hyperplasia) within the fibroadenoma was found in 32.3% of cases. Carc inoma in situ (CIS; 5 ductal, 3 lobular) was found in 8 fibroadenomas (2.0% ) removed from 6 patients, the youngest of whom was 40 years of age. In 3 c ases CIS was not confined to the fibroadenoma, but also involved the adjace nt parenchyma. No invasive carcinoma was present within this series. Comple x histologic features were seen in 40.4% of cases, mostly in relatively old er patients (mean age, 35.4 years). Hyperplasia in adjacent tissue was foun d in 8.8% of cases, usually in older patients (mean age 45.5 years). Known risk-elevating lesions in and around breast fibroadenomas occur frequently and mostly in patients older than 35 years. These findings may have consequ ences for the clinical management of a subgroup of patients with fibroadeno ma.