A clinicopathological study of fibroadenomas with epithelial proliferation including lobular carcinoma in-situ, atypical ductal hyperplasia, DCIS and invasive carcinoma.

Background: Fibroadenoma is a benign mixed tumor composed of epithelial and non-epithelial components. The epithelial component of a fibroadenoma may exhibit proliferation, including lobular carcinoma in-situ, atypical ductal hyperplasia, DCIS and rarely, invasive breast carcinoma.

Objective: In this series of 30 cases of fibroadenoma with epithelial proliferation, we assessed the radiological and histopathological findings of each entity.

Method: A retrospective review was performed to identify all fibroadenomas diagnosed at our institution between January 2012 and May 2018.

Results: In a total of 1523 consecutive cases of fibroadenomas, thirty cases had epithelial proliferations with an overall prevalence of 1.97%. Eight cases had fibroadenoma with lobular carcinoma in-situ, six cases had atypical ductal hyperplasia, ten cases had DCIS and six cases had invasive carcinoma. In cases of fibroadenomas with lobular carcinoma in-situ, 62.5% of the cases the neoplasia was confined to the fibroadenoma whereas only 10% of the cases with DCIS showed confinement to the fibroadenoma (p = 0.036). The most common radiological finding was the presence of a mass. The BI-RADS scores were 4 and above in all cases (p > 0.05).

Conclusion: In our study population, the most common type of carcinoma arising in fibroadenomas was DCIS, followed by lobular carcinoma in-situ. Lobular carcinoma in-situ was more likely to be confined to the fibroadenoma while most DCIS involved surrounding breast tissue.