Cancer is a disease in which cells grow in an abnormal way. Normally, the cells divide in a controlled manner. If cells keep dividing when new cells are not needed, a mass of tissue called a tumor forms.

A tumor can be benign or malignant. A benign tumor is not cancer and will not spread to other parts of the body. A malignant tumor is cancer. Cancer cells invade and damage tissue around them. They can also enter the lymph and blood streams, spreading to other parts of the body. Testicular cancer is the development of malignant cells in one or both testicles.

Cancer Cell Growth

Copyright © Nucleus Medical Media, Inc.

The testicles (or testes) are a pair of male sex glands. They are located under the penis in a sac-like pouch called the scrotum. The main functions of the testicles are to produce hormones (androgens) that control sexual development, reproduction, and sperm production. Immature sperm cells migrate through a network of tiny tubules called the epididymis. Sperm cells are stored and mature in this structure. During ejaculation, sperm cells move through the vas deferens, into the urethra, and out of the body.

Male Reproductive Organs

Copyright © Nucleus Medical Media, Inc.

Cell division and cell death are a normal process in the body to replace old or damaged cells. Changes in hormones, which may or may not be affected by genetic abnormalities, cause changes in testicular cells. These changes can alter the DNA of the cells which tells them when to grow and when to stop. Normally the cells only grow enough to replace old or damaged cells but damaged DNA may cause the abnormal growth of cells, known as cancer.

Testicular cancer can start anywhere in the testicular tissue. but the most common place is in the germ cells that make sperm. Testicular cancer can spread directly to nearby structures and into abdominal cavity. The cancer can also spread to adjacent lymph nodes or blood vessels, which can carry cancer cells to other areas of the body. The most common sites for testicular cancer to spread are to lymph nodes in other parts of the body and the lungs.

Testicular cancer is characterized by where tumors start, the types of cells affected, and their appearance under a microscope. Over 90% testicular cancers are germ cell tumors. Germ cell tumors include:

  • Seminomas—Tend to grow more slowly than other types and include:
    • Classical—Make up over 95% of seminomas.
    • Spermatocytic—Rare type that tends to occur in men over 60 years old.
  • Non-seminomas arise from other cells in testicular tissue. They tend to grow faster and spread outside of the testicle more than seminomas. Non-seminomas are rare and include:
    • Embryonal
    • Yolk sac—Most common in infants and children.
    • Choriocarcinoma
    • Teratoma

Some types of testicular cancers are a mix of different types of cells.