Fine needle aspiration of benign and malignant breast masses associated with pregnancy.

Of 1,612 fine needle aspirates (FNA) of breast lesions performed over a seven-year period, 25 cases (1.5%) were identified as breast masses associated with pregnancy. Patients ranged in age from 16 to 46 years, with a mean of 27. Gestational age at the time of FNA ranged from three months to three months postpartum or following breast-feeding. Cytologic diagnoses of these pregnancy-associated breast masses were: galactocele (5 cases, 20%), lactating adenoma (9 cases, 36%), fibroadenoma with lactational change (7 cases, 28%), juvenile fibroadenoma with lactational change (1 case, 4%), atypical reactive duct cells with lactational change (1 case, 4%) and infiltrating duct carcinoma (2 cases, 8%). The degree of lactational change varied proportionately with gestational age. None of the 22 patients with benign cytologic diagnoses of galactocele, lactating adenoma or fibroadenoma subsequently developed carcinoma. The mean clinical follow-up for these 22 patients was 27 months. Three cases of fibroadenoma and the case of juvenile fibroadenoma were confirmed by surgical excision. Biopsy of the lesion cytologically diagnosed as atypical reactive duct cells with lactational change revealed infiltrating duct carcinoma (IDC). All three patients with IDC had involvement of multiple axillary lymph nodes, and 1 patient had widely metastatic disease. In two cases of IDC the background lactational breast epithelium exhibited marked cytologic atypia that closely resembled the IDC. Pregnancy-related cellular atypia potentially results in a false-positive diagnosis of breast carcinoma on FNA. FNA is useful in distinguishing benign breast masses of pregnancy from those with marked cytologic atypia requiring surgical biopsy and may minimize the delayed diagnosis of carcinoma associated with pregnancy.