A hard bag on the chest is considered to be due to folliculitis, keloid, lipoma and other factors. 1. Folliculitis: this is an inflammatory skin disease mainly involving hair follicles, usually occurring in the sebaceous gland secretion of the parts, such as the chest, often manifested as a red papule centered on the hair follicle, may be accompanied by itching and pain symptoms. 2. Keloid: usually caused by excessive proliferation of skin fibrous tissue, mainly secondary to skin trauma or local skin infections, the scar will be higher than the skin surface, tough texture, nodular, striated or flaky. 3. Lipoma: this is a common soft tissue benign tumor, may occur in any fatty parts of the body, including the chest, mainly due to the mature fat cells, can be located in the subcutaneous confined mass, can also be seen in the deep part of the body. There may be other reasons for the growth of a hard lump on the chest, so it is necessary to cooperate with the doctor to improve the examination to determine the cause before treatment and therapy.