You won’t know if you have brain cancer until your doctor has talked to you, completed an examination and done some tests. The tests might include: a physical examination a lumbar puncture, also called a spinal tap, where a needle is put into your back to collect some fluid near the spinal cord to test for cancer cells imaging tests like an ultrasound, a CT scan or MRI scan to see what your insides look like Taking a sample from the tumour, called a biopsy, for examination under the microscope.Most people who have these tests find out they don’t have cancer. But it’s really important to check.