A hard lump on the chest is a common clinical cause of sebaceous cysts, keloids, and dermatofibromas. 1. Sebaceous cysts: the cause of this disease is that the sebaceous gland ducts in the skin are blocked, resulting in the gradual accumulation of sebum and the formation of retention cysts, which are most common in the head, face, back and buttocks and other parts of the body, the clinical manifestations of the surface of the body as a mass, the mass of the nature of the hardness of the medium or elasticity, smooth surface, clear boundaries, and so on. 2. Keloid: this disease is also known as connective tissue hyperplasia, which is a kind of pathological scar tissue secondary to skin trauma or spontaneous formation of overgrowth, usually associated with trauma, postoperative complications and other factors, the clinical manifestations of the skin surface above the rope or swelling. 3. Dermatofibroma: this disease refers to a kind of benign tumor in the dermis caused by the proliferation of fibroblasts or histiocytes, which is mostly seen in young and middle-aged women, with the clinical manifestation of round or ovoid solid nodules on the skin surface, and the surface of the nodules is rough or smooth. If the above condition exists, it is recommended to consult a doctor for a clear diagnosis and further treatment.