Double breast development may or may not be breast cancer. 1. Breast cancer: Breast cancer can also occur on both sides of the breast at the same time or successively, which will lead to the development of double breasts. Breast cancer is a serious disease, which often requires mastectomy, and it is recommended to diagnose and treat it as early as possible. 2. Non-breast cancer: Non-breast cancer diseases of both breasts include bilateral mastitis, bilateral breast hyperplasia, bilateral breast fibroma, etc. These diseases are breast diseases that are easy to occur, and are more common in women’s lives, so they need to pay more attention to them. Gynecomastia is a common type of disease in women. Women are advised to go to the hospital regularly for breast examination.