Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

Testicular Cancer

What Is It?

Testicular cancer is the uncontrolled growth of abnormal cells in one or both testicles (testes). The testicles are the male sex glands. They are located in the scrotum, behind the penis. They produce testosterone and other male hormones. They also produce and store sperm, the male reproductive cells.

Once testicular cancer develops, it can remain within the testicle, or it can spread to lymph nodes in the abdomen. If it is not detected, testicular cancer eventually can spread to the lungs, brain, liver and elsewhere.

In 2008, about 8,100 men will be diagnosed with testicular cancer in the United States. Most will be between the ages of 20 and 40. Though testicular cancer makes up only 1% of all cancer cases in men, it is the most common cancer in younger men.

Testicular cancer is more common in whites than blacks. Men with a history of undescended testicle (cryptorchidism) have an increased risk for testicular cancer. About 10% of all testicular cancers are found in this group of men. Also, men who have developed cancer in one testicle have a 2% to 3% lifetime risk of developing cancer in the other testicle.

Other men also are at increased risk for testicular cancer:

• Men with a family history of testicular cancer

• Men with an undeveloped testis

• HIV positive men

• Men with certain genetic conditions, such as Down syndrome or Klinefelter syndrome

There is speculation about whether these conditions also increase risk:

• Mumps infection of the testicle

• Maternal exposure to diethylstilbestrol

• Exposure to Agent Orange

Sometimes, testicular cancer is found when a man is being evaluated for infertility.

There are two main types of testicular tumors:

• Germ cell tumors — Most testicular cancers — about 95% — start in germ cells. These are the cells that form sperm. There are two types of germ cell tumors:

  • Seminomas (40% of all testicular cancers) tend to grow slowly. They usually stay within the testicles for a long time without spreading.

  • Non-seminomas (55% of all testicular cancers) form in more mature germ cells. They are more likely to spread, especially to lymph nodes. Lymph nodes are bean-shaped structures throughout the body that produce and store infection-fighting cells.

• Tumors of supportive tissues — About 5% of testicular cancers begin in the testicles' supporting tissues. These cancers are called Sertoli cell tumors and Leydig cell tumors.