Do we know what causes testicular cancer?

The exact cause of most cases of testicular cancer is not known. But scientists have found that the disease is linked with a number of other conditions, which are described in the section called "What are the risk factors for testicular cancer?" A great deal of research is being done to learn more about the causes.

During the past few years, researchers have learned a lot about certain changes in chromosomes and DNA that may cause normal testicular germ cells to develop into germ cell tumors. Chromosomes are long strands of DNA and protein that carry genetic information about inherited traits. Each sperm or egg cell has half as many chromosomes as other body cells. So when the sperm and egg combine, the resulting embryo has a normal number of chromosomes, half of which are from each parent. This is why we tend to look like our parents.

Meiosis is the process by which germ cells with 46 chromosomes develop into sperm or egg cells with 23 chromosomes. Testicular germ cell tumors may form when something abnormal happens during meiosis. Instead of forming normal sperm cells with 23 chromosomes, all 46 chromosomes remain. Usually, these chromosomes become unstable and progressively more abnormal in their shape and number (often between 69 and 82) as the cells continue to divide. Testicular cancer cells often have extra copies of a part of chromosome 12 (this is called isochromosome 12p). Scientists are studying DNA from this chromosome to learn more about exactly what goes wrong during meiosis and how this might be prevented or reversed.

Several other abnormal chromosomes and changes in the factors that regulate cell division and the cell cycle have been associated with testicular cancer, both in animals and in humans. All of these changes are being studied to find the true causes of testicular cancer.