You have a bone marrow test to check whether there are cancer cells in your bone marrow. Bone marrow is spongy tissue and fluid that is inside your bones. It makes your blood cells. You may also have this test to check how well your treatment is working.
A doctor or specialist nurse removes a sample of bone marrow cells or an area of bone marrow in one piece. This is usually from your hip. A specialist doctor can then look at the cells or tissue under a microscope.