Different tests may be needed to diagnose a germ cell tumour. Usually, the doctor will remove a sample of tissue from the lump (a biopsy) for examination under a microscope to find out if it is a cancer or not. CT or MRI scans may be used to see the exact position of a tumour within the body. Chest X-rays may be taken to see if there’s a tumour in the lungs. Germ cell tumours often produce proteins called tumour markers that can be measured in the blood. The ones that are produced by germ cell tumours are alpha-fetoprotein (AFP) and human chorionic gonadotrophin (HCG). Your child will have blood tests to check these tumour markers when they are being diagnosed. The doctors will continue to check these during treatment and after treatment is over. Sometimes a germ cell tumour can be diagnosed with a tumour marker and scan results so that a biopsy isn’t necessary. This is particularly so if surgery is not needed for treatment, for example if the tumour is in the brain.