Fibromatosis of the breast is similar to fibromatosis elsewhere in the body (e.g., desmoid tumors).

Clinical Features
Patients can present with a palpable mass that mimics carcinoma and is sometimes associated with skin retraction or fixity to underlying muscle.

Radiology
On mammography, these lesions are indistinguishable from carcinoma.

Pathology
Macroscopic Appearance
These lesions vary in size from 0.7-10 cm. They are poorly circumscribed, vary in color from gray/pink to white and have a fibrous consistency.

Microscopic Appearance
Most lesions are composed of a uniform population of spindle cells that are arranged in interlacing bundles that surround and entrap breast parenchymatous structures. At the periphery, the lesion may have an infiltrative interface with adjacent structures. The cells lack atypical features. Mitotic figures may be present but are uncommon. Collections of lymphocytes are frequently present at the periphery of the lesion.

Management
Wide-local excision is the treatment of choice. Inadequate excision often leads to local recurrence.

A.D. Purushotham, P. Britton and L. Bobrow
A prospective study of benign breast disease and the risk of breast cancer. JAMA 2002

References