Breast, Fibroadenoma and sclerosing adenosis

Fibroadenoma is one of the most common benign breast neoplasms. It is characterized by a biphasic proliferation of ducts and stroma, and is usually managed conservatively. In this case, the fibroadenoma is associated with sclerosing adenosis, making it a complex fibroadenoma. Complex fibroadenomas habour one or more complex change(s) including cysts (> 3mm in diameter), sclerosing adenosis (as in this case), epithelial calcification or papillary apocrine changes. It has a slightly increased risk of malignancy; however, the risk remains low and can be managed similar to a simple fibroadenoma.

Sclerosing adenosis is a lobulocentric proliferation of acini around a central duct. Lumina are frequently compressed by surrounding sclerosis, mimicking invasive ductal carcinoma. This can be resolved by a simple immunohistochemical stain for myoepithelial cell layers such as p63 or smooth muscle myosin heavy chain, which will be retained in sclerosing adenosis and lost in invasive ductal carcinoma.