Germ cell tumours can appear at any age. They develop from cells that produce eggs or sperm so germ cell tumours can affect the ovaries or testes. However, it is also possible for a germ cell tumour to develop in other parts of the body.
As a baby develops during pregnancy, the cells producing eggs or sperm normally move to the ovaries or testes. However, rarely they can settle in other parts of the body where they can develop into tumours. The most common places for this to happen are the bottom of the spine (sacrococcygeal), the brain, chest and abdomen.
Germ cell tumours are sometimes given different names based on what they look like under the microscope. These include yolk-sac tumours, germinomas, embryonal carcinomas, mature teratomas and immature teratomas.
They may be non-cancerous (benign) or cancerous (malignant). Malignant tumours have the ability to grow and spread to other parts of the body. Benign tumours do not spread but may cause problems by pressing on nearby tissue and organs. Immature teratomas fall between benign and malignant. They can occur at many different sites, most commonly in the abdomen and can spread locally, such as within the abdomen, but rarely beyond. They can usually be removed with an operation.