Testicular cancer occurs when cells that aren't normal grow out of control in the testicles (testes). It is highly curable, especially when it is found early.

The testes are the two male sex organs that make and store sperm. They are located in a pouch below the penis called the scrotum. The testes also make the hormone testosterone.

Testicular cancer is rare. But it is the most common cancer among young men.

Most testicular cancers start in cells that make sperm. These cells are called germ cells. The two main types of testicular germ cell cancers are seminomas and nonseminomas. Seminomas grow and spread slowly and respond to radiation therapy. Nonseminomas grow and spread more quickly than seminomas. There are several different types of nonseminomas.