Fibrous lesions of the breast: imaging-pathologic correlation.

Fibroepithelial lesions of the breast are commonly seen in clinical practice. The masses are composed of a combination of prominent stroma and varying glandular elements. Fibroadenomas, benign lesions that derive from the terminal duct lobular unit, are the most common and are often identified at clinical examination or mammography as circumscribed masses. Benign mesenchymal tumors include focal fibrosis, pseudoangiomatous stromal hyperplasia, and fibromatosis or desmoid tumor. Phyllodes tumor, which is similar to fibroadenoma but has increased cellularity in the stroma, is typically benign but has malignant potential. Diabetic fibrous mastopathy, a stromal proliferation found in patients with juvenile-onset insulin-dependent diabetes, is a reactive fibrous lesion. Most of these lesions manifest as masses at clinical and/or mammographic examination. Some (eg, fibroadenomas) may be associated with calcifications. Except for fibromatosis and phyllodes tumor, fibroepithelial lesions need not be excised if the diagnosis is confirmed by the results of histologic analysis at percutaneous biopsy. To correctly differentiate between fibrous breast lesions that are benign and those that should be resected, the physician must be familiar with the correlated radiologic-pathologic findings in the various lesion types. RSNA, 2005.