The most common benign disorder, fibrocystic change, affects 40–50% of premenopausal women It is a unified term for several proliferative, but nonneoplastic parenchymal alterations, which are usually bilateral and multifocal (Tavassoli 1992). The histologic pattern in each case is varying and may include pure fibrocystic lesions (duct ectasia, cysts, fibrosis, adenosis, ductal epithelial proliferation), focal fibrosis, ductal and lobular epithelial hyperplasia (also atypical) and microcystic and fibrous mastopathy due to involutional change
Fibroadenoma is the most common tumor in young and adolescent women. It arises as a localized hypertrophy of the TDLU and contains structures resembling terminal ducts and expanded stromal tissue . Both the stroma cellularity and the epithelial component of fibroadenoma varies, which may lead to misinterpretations in differential diagnosis between fibroadenoma and phyllodes tumor or carcinoma (Rosen 2001).
After menopause, fibroadenomas degenerate and may develop large, coarse calcifications. Multiple tumors occur in about 15% of cases, and sometimes the tumor may grow to involve the whole breast, known as adolescent giant fibroadenoma Carcinoma may develop in a fibroadenoma in 1–2% of cases (
Phyllodes tumor, previously known as cystosarcoma phyllodes, arises from periductal stroma and contains sparse lobular elements (Rosen 2001). Increased cellularity of the stromal components is characteristic and separates phyllodes tumor from fibroadenoma.
Although usually benign, some tumors show increased mitotic activity, pronounced overgrowth of the stroma and aggressive peripheral growth, turning it into malignancy
Papilloma arises in the duct epithelium as papillary projections with or without fibrous cores It is usually a solitary tumor, but may also present as multiple lesions (Sewell 1995). The term intraductal papilloma refers to a lesion in a cystically dilated duct . Clinically, papilloma often becomes evident because of nipple discharge, which may be bloody or non-bloody (Rosen 2001). It is a low-risk lesion, but may develop atypical and precancerous cell populations
Radial sclerosing lesion, also known as radial scar is usually an incidental finding at mammography and presents as a stellate lesion mimicking cancer. It is a benign lesion with a central fibrous core surrounded by contracted ducts and lobules, which may show different types of proliferation including atypic and precancerous changes . The etiology is unproved, but it has been presented that it might be due to an inflammatory process resulting in scar formation or slow infarction
Ductal hyperplasia has no specific clinical or pathologic features, and it does not usually present as a palpable tumor. Microscopically, there is epithelial proliferation in the ductal system and it is often present in tissue with fibrocystic changes . Atypical ductal hyperplasia refers to a monoclonal neoplastic proliferation within a ductus already occupied by ordinary hyperplasia . It is close to intraductal carcinoma, but does not fulfill all the criteria
In puerperal mastitis, accumulation of milk provides a microenvironment for bacterial (usually Staphylococcus aureus) growth. Without treatment it may lead to abscess formation. In chronic state, fistulas are seen. The pathogenesis is uncertain and histologic findings depend on chronicity of the process . Plasma cell mastitis is a form of periductal mastitis characterized by an intense plasmasytic reaction to retained secretion in the ducts. Histologically, there is hyperplasia of duct epithelium surrounded by plasma cell infiltrate. Both the acute and mature phases may be difficult to distinguish from carcinoma