There is a hard bag in the middle of chest mostly for chest wall subcutaneous tissue lesions, but also may be rib cartilage disease or sternal developmental abnormality, but also may be the deformity of sternal fracture after healing. 1. Chest wall subcutaneous tissue lesions: there is a hard bag in the middle of the chest most commonly found in chest wall subcutaneous tissue lesions such as lipoma, fibroma, sebaceous cysts, etc., which can be removed by local anesthesia surgery. 2. Diseases of rib cartilage or abnormal development of sternum: such as costochondritis, costochondral deformity, chicken breast, etc., which cause enlarged rib cartilage or deformity of anterior convexity of sternum, and there is a hard bag in the middle of chest. 3. The deformed healing of sternal fracture can also lead to the appearance of a hard bag in the middle of the chest. It is recommended to go to the hospital for further diagnosis and treatment of a hard bag in the middle of the chest.