Your risk of developing cancer depends on many factors. This includes things like whether you smoke and have a healthy balanced diet, as well as genetic and environmental factors. 

We don't know what causes most cases of testicular cancer. But there are some factors that may increase your risk of developing it.  

Having one or more risk factors doesn't mean that you will definitely get testicular cancer. As testicular cancer is rare, the risk of developing it is small even if you do have any risk factors.

Causes of testicular cancer

It's not clear what causes most testicular cancers.

Testicular cancer starts when something causes changes to the DNA of testicle cells. A cell's DNA holds the instructions that tell the cell what to do. The changes tell the cells to grow and multiply quickly. The cancer cells go on living when healthy cells would die as part of their natural life cycle. This causes a lot of extra cells in the testicle that can form a mass called a tumor.

In time, the tumor can grow beyond the testicle. Some cells might break away and spread to other parts of the body. Testicular cancer most often spreads to the lymph nodes, liver and lungs. When testicular cancer spreads, it's called metastatic testicular cancer.

Nearly all testicular cancers begin in the germ cells. The germ cells in the testicle make sperm. It's not clear what causes DNA changes in the germ cells.

Risk factors of testicular cancer

Factors that may increase your risk of testicular cancer include:

• Having an undescended testicle, which is called cryptorchidism. The testes form in the belly during fetal development. They typically descend into the scrotum before birth. If you have a testicle that never descended, your risk of testicular cancer is higher. The risk is increased even if you've had surgery to move the testicle to the scrotum.
• Having a family history of testicular cancer. If testicular cancer runs in your family, you might have an increased risk.
• Being a young adult. Testicular cancer can happen at any age. But it's most common in teens and young adults between 15 and 45.
• Being white. Testicular cancer is most common in white people.