33 Special Types of Invasive Breast Carcinoma: Diagnostic Criteria ...

solid, grayish white, and bulging, with a whorl-like pattern and slitlike spaces;
necrosis is rare.
Morphologic variations found in fibroadenoma include the following:
1. Stromal hyalinization, calcification, or ossification, especially with aging,
2. Focal stromal multinucleated giant cells,
3. Areas of stromal mature fat, smooth muscle, myxoid change, or cartilage (61-64),
5. Areas of squamous metaplasia, but phyllodes tumor should be ruled out,
6. Focal lactational changes, not necessarily associated with pregnancy or nursing,
7. Focal infarction, which is rare but usually associated with pregnancy,
8. Irregular or ill-defined margins that blend or admix with surrounding fibrocystic
breast tissues, suggesting multifocality (this form has been designated
fibroadenomatosis or fibroadenomatoid hyperplasia, and may explain some
recurrences),
9. Areas of apocrine metaplasia,
10. Areas of sclerosing adenosis (i.e., mixed fibroadenoma–sclerosing adenosis
tumor),
11. "Complex" fibroadenoma change, which has been used when fibroadenomas have
cysts, sclerosing adenosis, calcifications, or papillary apocrine changes.
So-called juvenile fibroadenoma is associated with young age, large size, and
hypercellularity (64-74). The juvenile fibroadenoma occurs in adolescents (often in
blacks and sometimes involving both breasts), reaches a large size (even up to 10 cm),
and shows hypercellularity of glands or stroma. These attributes can be found
independently of each other, but there is clearly a link between them. Various names
have been applied to these lesions, including juvenile fibroadenoma (63, 72, 73), giant
or massive fibroadenoma, cellular fibroadenoma (73, 74) and fibroadenomas with
atypical epithelial hyperplasia (72).Distinguishing cellular fibroadenoma from benign
phyllodes tumor may be more of an academic exercise than a practical one, since both
are easily managed by conservative local therapy, even with recurrence (64-74).
Malignant change in fibroadenomas is found in approximately 0.1% of the cases (75,
76) and involves the epithelial component in more than 90% (75-79). Carcinoma in
situ within fibroadenoma can be of the lobular or the ductal type; both occur with
nearly equal frequency (75). I and others (69) have seen benign fibroadenoma develop
into osteosarcoma.
Sclerosing adenosis has a broad spectrum of presentations that can mimic may be
associated with a 1.7-fold increased risk for the development of invasive breast
cancer. These authors included sclerosing adenosis in the group of histopathologically
defined lesions termed proliferative breast disease (or changes) without atypia, which
89