The lesion consists of enlarged mammary lobules with an increased epithelial to stromal ratio, manifest by an increased proliferation of ductules. There is both interlobular stromal fibrosis as well as more prominent intralobular fibrosis (the normal slightly blue myxoid stroma within lobules is completely lost and instead hyalinized).

The cytology is bland and all the ductules are surrounded by myoepithelium.

The duct lumens are open and patent, resembling the pericanalicular pattern of fibroadenomas

Here we see a trichrome stain which highlights the extensive stromal fibrosis

First described in the mid 1980's, sclerosing lobular hyperplasia (SLH) describes a benign sclerosing lesion of young women closely related (and possibly a precursor) to fibroadenoma, characterized by extensive lobular hyperplasia with both intra and interlobular stromal fibrosis.

Fibroadenomas may arise from SLH via a localized and accelerated proliferation/overgrowth of ductal epithelium, and many use the term fibroadenomatoid mastopathy synonymously with SLH.

Present similarly to fibroadenoma, and most of the time the preoperative diagnosis is either fibroadenoma or fibrocystic changes. Usually seen either in adolescent or young women (mean age 28-32yrs).

Complete excision is curative.

Completely benign, although recurrence as a fibroadenoma rarely occurs.

- Can resemble "miniature" fibroadenomas