Hard lumps on the foreskin may be caused by circumcision, epidermal cysts, penile cancer and other diseases. 1. Circumcision: the etiology of circumcision may be related to congenital development, trauma, local inflammation and other factors, obesity, poorer hygiene and other reasons may also induce the disease. In case of prepuce, due to the accumulation of shed cells in the prepuce cavity, under the action of inflammation, it may lead to prepuce stones, thus making hard lumps on the prepuce. 2. Epidermal cysts: Epidermal cysts are cysts containing keratin within the dermis, and the etiology may be related to skin injury, embryonic ectopic sex and other factors. The patient will have nodules locally, which are round, hard and can be pushed slightly by hand, and can be seen in any part of human body. 3. Penile cancer: penile cancer is a tumor originated from the head of penis and inner mucous membrane of prepuce, the cause of which may be related to HPV infection, poor hygienic habit, long prepuce and other factors. The main manifestation is a lump at the foreskin, usually cauliflower-shaped, which may cause difficulty in urination. For patients with hard lumps on the foreskin, it is recommended to go to a regular hospital for examination to clarify the cause.