Cysts on the penis may be sebaceous cysts, and may also be caused by penile cancer, condyloma acuminatum and other diseases, which should be promptly consulted to find out the causes. 1. Sebaceous cyst: its cause may be formed by excessive secretion of sebaceous glands and obstruction of ducts. 2. Penile cancer: penile cancer is a malignant tumor occurring in male penis, patients may have penile swelling, which is usually hard in texture, accompanied by clinical manifestations such as penile ulceration, pain, abnormal secretion, etc. In advanced stage, patients may also have systemic symptoms such as emaciation, anemia and loss of appetite. 3. Condyloma acuminatum: mainly caused by human papilloma virus infection of sexually transmitted diseases, men are mostly seen in the penis, glans, perineum, etc., may also appear penis lumps, usually soft texture, after gradually increase, can be cauliflower-shaped, accompanied by erosion, oozing, bleeding and infection. Patients found penile cysts, there may be other reasons, it is recommended to actively seek medical attention, under the guidance of a professional physician.