Testicular cancer occurs in the testicles (testes), which are located inside the scrotum, a loose bag of skin underneath the penis. The testicles produce male sex hormones and sperm for reproduction. Compared with other types of cancer, testicular cancer is rare. But testicular cancer is the most common cancer in American males between the ages of 15 and 35. Testicular cancer is highly treatable, even when cancer has spread beyond the testicle. Depending on the type and stage of testicular cancer, you may receive one of several treatments or a combination.