Testicles have 2 main functions:
1/ They make male hormones (androgens) such as testosterone.
2/ They make sperm, the male cells needed to fertilize a female egg cell to start a pregnancy.
Cancer that starts in the testicles is called testicular cancer. Testicles (also called the testes) are part of the male reproductive system. These 2 organs are each normally a little smaller than a golf ball in adult males and are contained within a sack of skin called the scrotum. The scrotum hangs beneath the base of the penis.
The testicles are made up of several types of cells, each of which can develop into one or more types of cancer. It is important to distinguish these types of cancers from one another because they differ in how they are treated and in their prognosis.
Cancer starts when cells in the body begin to grow out of control. Cells in nearly any part of the body can become cancer, and can spread to other areas of the body.