Fibroadenoma of the breast: analysis of associated pathological entities--a different risk marker in different age groups for concurrent breast cancer.

BACKGROUND: Fibroadenoma, one of the most common benign breast lesions, has a characteristic age-specific incidence and is associated with other pathological entities in 50% of cases. The clinical or imaging diagnosis of fibroadenoma may be erroneous, and in some cases is found to be invasive cancer. The clustering of such entities, their correlation with age, and the risk of synchronous breast malignancy are uncertain.
OBJECTIVE: To explore the possibility of any significant clustering of fibroadenoma-associated benign breast diseases and to assess the possible risk of concomitant breast cancer.
METHODS: We analyzed the pathological results of 147 women undergoing excisional biopsies for fibroadenoma diagnosed pre-operatively either by clinical examination and imaging (n = 17) or by radiology alone (n = 30). The inter-relationships among all entities associated with fibroadenoma were studied by hierarchical cluster analysis. The correlation of the various pathologies with the risk of invasive breast cancer in relation to the patient's age was also evaluated.
RESULTS: Fibroadenoma-associated pathologies were found in 48% of the cases: sclerosing adenosis (23%), duct ectasia (17.7%), apocrine metaplasia (15.6%), florid fibrocystic disease (12.9%), duct papillomatosis (11.6%), infiltrating duct carcinoma (5.4%), duct carcinoma in situ (3.4%), and 1 case of lobular carcinoma in situ (0.6%). An orderly internal hierarchy and three significant clusters emerged: a) epithelial apocrine metaplasia, duct ectasia and sclerosing adenosis (similarity coefficients 16.0, 11.0 and 8.0 respectively); b) papillomatosis, florid fibrocystic disease and calcifications (similarity coefficients of 6.0, 4.0 and 2.0 respectively); and c) infiltrating duct carcinoma and duct carcinoma in situ (similarity coefficients of 1.8 and 1.6 respectively). Seven of the eight patients with breast cancer were older than 40 years.
CONCLUSIONS: In about half of the cases fibroadenoma was associated with other pathological entities clustered in an orderly hierarchy. The rarity of synchronous breast cancer in the younger age group and its more common association with fibroadenoma in the older age groups dictate a different approach to each. The finding of fibroadenoma in women older than 40 indicates the need for surgical excision.