Testicular cancer develops in the testicles (testes), the male reproductive glands. The testicles are located in the membranous pouch below the penis (scrotum) and are suspended from the body by the spermatic cord. They produce male reproductive cells (sperm) and testosterone. Testicular cancer is treated successfully in more than 95% of cases.

Most (95%) testicular cancer originates in undeveloped cells (germ cells) that produce sperm. These tumors, called germ cell tumors (GCTs), are most common in men between the ages of 20 and 40 and are curable in more than 95% of cases. There are two main types: seminomas and nonseminomas. A third type, called stromal tumors, develops in the supporting tissues of the testicle.