The correlation of histologic changes in the human breast with the menstrual cycle

Histologic changes in the normal human mammary gland associated with the menstrual cycle were sought in tissues derived from a defined population of patients undergoing subcutaneous mastectomy or reduction mammoplasty for reasons other than neoplasia. Ninety patients were selected for their regular menstrual cycling, abstinence from hormone use, and absence of disease which might influence pituitary-ovarian cycling. Morphologic changes in the mammary stromal and epithelial components were identified as they related to specific pituitary-ovarian events, and histologic criteria were identified that allowed reproducible morphologic categorization of the mammary gland into five specific phases: proliferative (Days 3-7); follicular phase of differentiation (Days 8-14); luteal phase of differentiation (Days 15-20); secretory (Days 21-27); and menstrual (Days 28-2). Double-blind reviews of tissues confirmed the validity and the reproducibility of these histologic criteria in identifying the menstrual phase. The findings further characterize the morphologic correlates of hormone responsiveness of the normal human mammary gland. The recognition of menstrual-cycle-dependent histologic changes may be expected to provide a basis for extending the interpretation of the morphologic characteristics of the breast in surgically acquired specimens that may be associated with hormonal aberrations.