Bone bulge under one breast may be related to trauma, congenital deformity of rib development, chondroma and other reasons. 1. Trauma: Trauma to the ribs leads to fracture, if the fracture end is displaced, it can be manifested as a bone bulge under one breast. 2. Congenital rib deformity: fetal position and maternal factors can cause abnormalities in the development process, which will lead to congenital rib deformity. 3. Chondrosarcoma: Its typical symptoms are painless swelling and deformity, and if it occurs in the rib cage, it may lead to a bone bulge under one side of the breast. It is recommended that the person who has a raised bone under one side of the breast should go to the hospital in time, clarify the cause of the disease, and carry out standardized treatment under the guidance of the doctor, so as to avoid delaying the condition.