38-year-old male right breast is bigger than the left side of the cause, can be seen in obesity, may also be male breast development, local trauma caused by, should be timely consultation to identify the cause of the disease. 1. Obesity: Obesity can cause excessive fat in the male breasts, resulting in inconsistent size of the male bilateral breasts, thus appearing in the male right breast than the left. 2. Gynecomastia: It may be due to various reasons that the proportion of estrogen and androgen in the male body is imbalanced, which leads to the abnormal proliferation of breast tissue, development of a disease, the performance of which is the enlargement of breasts, which may lead to the situation that the right side of the male breasts is bigger than the left side. In addition, the hyperplasia of breast tissue may also be combined with breast fibroadenoma, breast cancer and other diseases. 3. Localized trauma: If the male breast is hit by an external force, a local hematoma may occur, resulting in the enlargement of the breast on one side. In addition, breast inflammation, trauma, tumors and chest wall diseases may also appear similar clinical manifestations, 38-year-old men appear right breast is larger than the left, it is recommended to go to the regular hospital for a systematic examination, in order to clarify the specific causes, according to the doctor’s advice to choose the most appropriate treatment.