Surgical treatment of gynecomastia in non-obese patients. I. What is gynecomastia? Gynecomastia presents as a tough, elastic lump under the nipple. This disc-shaped glandular tissue under the areola resembles a thread-like mass on palpation. It is clinically classified as: type 1: small breasts without skin redundancy; type 2a: medium-sized breasts without skin redundancy; type 2b: medium-sized breasts with skin redundancy; and type 3: large breasts with skin redundancy. The prevalence of the disease is 65% in adolescent males. II. What causes gynecomastia? Breast enlargement may be caused by glandular hyperplasia, increased fat (pseudobreast enlargement) or both. The pathophysiological cause of gynecomastia is thought to be an imbalance in the androgen balance, with a decreased testosterone to estradiol ratio. This imbalance can occur through multiple pathways and can directly affect breast tissue. Alterations in the ratio of estrogen to androgen, or an oversensitivity of the breast to circulating normal amounts of estrogen levels, all result in the proliferation, lengthening and branching of the milk ducts. This process is accompanied by the proliferation of fibroblasts and blood vessels. Patients are first screened by an endocrinologist, and those without hormonal abnormalities are treated surgically. Pre-operative ultrasound is routinely performed to assess glandular morphology and fat content. The goal of treatment is to remove excess fat and breast fibroglandular tissue, remove excess skin if necessary, and reconstruct a normal breast shape with minimal scarring. Vibrational liposuction is used to remove breast fat tissue from the chest wall, subareolar incisions are used to remove glandular tissue in normal weight patients with bilateral grade 1 or 2 gynecomastia, and the combined use of vibrational liposuction and surgical excision is also an effective method for treating non-obese patients. Although gynecomastia is a benign lesion, the psychological trauma it causes can have a long-term impact on the patient’s psychosocial state and social activities. Therefore, when reaching puberty, it becomes increasingly important to maintain a normal body shape, but it is not easy to achieve an optimal correction of the body shape.