A hard lump under the sternum may be related to the following reasons: 1. It may be a normal bony protrusion. In the lower part of the sternum, where the bilateral rib arches intersect, there is a saber protrusion, which is a normal bony protrusion of the human body. 2. There may be the effect of old fractures. If there is an old fracture here, it may produce a large amount of bone scab growth during its recovery process, which in turn leads to a bony hard mass. 3. There may be a case of a sclerotic liver. In some patients with cirrhosis, an enlarged, sclerotic liver may be palpable below the sternum. 4. There may also be an occupying disease, such as a tumor growth in the abdominal wall or abdominal cavity, where a hard mass may be palpable.