Testicular cancer is a disease caused by the uncontrolled growth of abnormal cells in the testicle.
This uncontrolled growth causes a lump or tumor. Cells can break away from the initial tumor to form new growths elsewhere in the body. Testicular cancer is most common in men under age 35 but can also occur in older men. The actual cause of testicular cancer is unknown. An abnormal growth of cancer cells in the testicle eventually causes the testicle to become enlarged or to develop a lump that can be seen or felt.