Gynecomastia, also known as gynecomastia or male gynecomastia, usually refers to the abnormal enlargement and development of breast tissue in men. Its incidence is high, reaching 32-65% in the male population. Its incidence varies among the male population at different ages: over 50% in newborns, up to 50-70% in adolescence, and up to 72% in middle-aged and older men aged 50-69. A variety of diseases and medications can cause gynecomastia, but most men have no obvious symptoms. For patients with clinical symptoms, such as pain in the nipple area or significant enlargement of the breast, most of them can be relieved to some extent by sex hormone-related medication, but there are still a significant number of patients who have serious psychological burden due to larger breasts, longer duration of the disease, and the lack of obvious efficacy of medication, such as not daring to go naked or wear thin clothing in summer; in addition, some men In addition, some men with gynecomastia have abnormal long-term breast tissue growth and may develop malignant changes to form breast cancer, which is often more malignant than female breast cancer, and these patients need early surgery to remove breast tissue for intervention. Gynecomastia is divided into four classes according to the degree of breast enlargement and the presence of excess skin: Class I, mild enlargement with no excess skin; Class II, moderate enlargement with no excess skin; Class III, moderate enlargement with excess skin; and Class IV, significant enlargement with significant excess skin, similar to adult female breasts. Gynecomastia can be divided into three types according to the ratio of breast parenchyma to adipose tissue in breast tissue: 1. Enlarged breasts are dominated by the proliferation of breast parenchyma; 2. Enlarged breasts are dominated by the proliferation of adipose tissue, mostly seen in obese men with enlarged breasts after weight loss; 3. Enlarged breasts have proliferation of both breast parenchyma and adipose tissue. Depending on the type of breast enlargement, different types of surgical interventions can be used clinically. For more information on how to treat gynecomastia and how effective the treatment is, please follow up with a subsequent article.