Immunohistochemical study of the relationship between Ki-67 labeling index of proliferating cells of gynecomastia, histological phase and duration of disease.

Gynecomastia is a benign proliferative lesion caused by various etiological factors and may result from a relative imbalance between serum estrogen and androgen levels. The histological alterations are similar, and gynecomastia can progress from a florid type to a fibrous type. The Ki-67 labeling index (LI) of gynecomastia specimen was investigated and higher Ki-67 LI was observed in florid and intermediate than in fibrous gynecomastia (P = 0.017). A correlation was found between the duration of disease and Ki-67 LI (P = 0.041): the shorter the duration the higher the Ki-67 LI. Thus, Ki-67 LI seems a useful tool to examine proliferation activity of gynecomastia and can assist in determination of appropriate treatment of gynecomastia with hormonal therapy.