[Adenoma of the breast: histopathological study of 9 cases].

Adenomas of the breast are cellular epithelial lesions, which are subclassified into two types, tubular adenomas (TA) and lactating adenomas (LA). In 3365 cases of benign epithelial tumors of the breast, including fibroadenomas, filed in the Hiroshima Tumor Tissue Registry between 1973 to 1985, only nine adenomas (TA-4, LA-5) or 0.3% were filed. All adenoma cases involved females, with an average of 27.4 years. Grossly, the tumors were found to vary from 1.5 to 5 cm in diameter and were sharply demarcated. Microscopically and ultrastructurally, the small tubules found in TA are identical to normal ducts. According to progress from pregnancy to lactation, the tubular tissue in LA demonstrate breast increasing secretory activities. The absence of TA during pregnancy, the structural similarity and the fact that some LA had already developed into a palpable mass before pregnancy are signs that indicate that all TA and LA share the same biologic process.