Hard bumps on the back are not called corns and may be due to conditions such as keloids and sebaceous cysts. Corns are a condition in which the skin thickens and involves the surrounding skin due to prolonged squeezing and friction, and are found on the feet, while those on the back are not called corns. Bumps on the back may be caused by keloids, sebaceous cysts and other conditions. 1. Keloid: a benign skin tumor caused by overgrowth of connective tissues in the skin, most patients have keloid physique, and some patients have family history. 2. Sebaceous cysts: If a hard and well-bordered lump appears on the back, it may be due to the gradual siltation of sebum and other sebum, forming cysts, often appearing on the back and buttocks, which can be removed by surgery. If there is any discomfort, you should actively go to the hospital for diagnosis and treatment.