Although little attention has been paid to fibro-adenomas of the breast observed during pregnancy and lactation, a study of these lesions is important since the changes seen are frequently confused with changes due to a malignant condition. Especially is such a study of interest in the light of the hormonal relationship of these lesions to the structure and function of the normal breast.
The term fibro-adenoma denotes an encapsulated fibro-epithelial lesion with either the pericanalicular or the intracanalicular type of connective tissue predominant.1 Nineteen cases of fibro-adenoma modified by pregnancy, including 9 of lactating adenoma or so-called cystadenoma (Billroth, 1860; Gross, 1879; Power, 1885; Speese, 1909, and others), have been reported in the literature (McFarland, 1922, 1927; Sudler. 1923; Ingleby, 1932; Cheatle and Cutler, 1931. and others). Several cases reported before 1900 which might properly belong to this group were rejected because the variance in terminology and the lack