Testicular Cancer. Testicular cancer is the most common cancer in men 15 to 35 years old. Testicular cancer is more common in white men than in black men.The causes of testicular cancer are not completely understood. But the following conditions increase the risk of development: 1  Undescended testicle.esticular Cancer. Testicular cancer is the most common cancer in men 15 to 35 years old. Testicular cancer is more common in white men than in black men.