•  This medium power view of several ducts shows the features of apocrine metaplasia.

•  The lining cells have abundant eosinophilic cytoplasm on the lumenal edge of the cell.

•  The nuclei are uniform and round.

• Secondary to an irregular response by breast tissue to hormonal stimuli

• May be due to relative or absolute excess of estrogen, decrease in progesterone, or abnormal response to either hormone by breast tissue

• 60-90% of breasts at autopsy

• Reproductive age women

• About 10% of women have clinically evident disease

• May be associated with tenderness and irregular nodularity which varies during the menstrual cycle

• Microcalcifications may be demonstrable on mammogram

• May be associated with epithelial hyperplasia or sclerosing adenosis although these entities should be reported separately

• Cysts, fibrosis, adenosis, and apocrine metaplasia do not elevate risk for breast carcinoma

• "Blue-dome" cysts which may be quite large

• Firm gray-white fibrous tissue

• Cysts containing inspissated secretions which may calcify

• Cysts may also contain macrophages; lined by flattened epithelium

• Apocrine metaplasia with columnar epithelium containing small nuclei and brightly eosinophilic cytoplasm

• Adenosis, or increased numbers of acini in the lobule, may be present.

• If ducts are enlarged in acini the term blunt duct adenosis is used.

• Robbins and Cotran: Pathologic Basis of Disease, 7th ed., 2005, p. 1127.

• Current literature from PubMed at National Library of Medicine