Adenomas of the breast and ectopic breast under lactational influences.

The tubular adenomas, lactating adenomas, and ectopic lactation- or gestation-associated benign lesions of the breast diagnosed during a 22-year period are reported. Forty-two breast adenomas (in 28 patients) that demonstrated lactational changes are reviewed, with special attention to classification and clinical presentation. Five ectopic lactating adenomas--three axillary or in the chest wall and two vulvar, the latter occurring in the same patient--were identified in three patients. The lesions in the remaining cases were fibroadenomas with lactational changes (16 patients) and lactating or tubular adenomas (nine patients). Striking histologic and clinical similarities between the tubular and lactating adenomas and the lesions identified as lactational changes within a fibroadenoma were observed, with foci of tubular adenomatous change present within otherwise typical fibroadenomas. The overlapping morphologic spectrum and the strong association with pregnancy or lactational influences blur the distinction between these entities and suggest a common pathogenesis. The cytologic features of lactational lesions of the breast and ectopic breast pose special problems in diagnosis by fine needle aspiration.