Seminomas make up about 30 percent of all testicular cancers. Nonseminomas are a group of cancers that include choriocarcinoma , embryonal carcinoma , teratoma, and yolk sac tumors . A testicular cancer may have a combination of both types. An estimated 7,400 men in the United States will be diagnosed with testicular cancer in 1999. Although testicular cancer accounts for only 1 percent of all cancers in men, it is the most common form of cancer in young men between the ages of 15 and 35.
Any man can get testicular cancer, but it is more common in white men than in black men.
The causes of testicular cancer are not known. However, studies show that several factors increase a man's chance of developing testicular cancer. Men who have had a testicle that did not move down into the scrotum are at greater risk for developing the disease. This is true even if surgery is performed to place the testicle in the scrotum. Men whose testicles did not develop normally are also at increased risk.