Does white cell count increase if a person has cancer?

Depends on type: The white blood cell count increases with leukemia which is an excessive proliferation of immature white cells. Thus, on the blood tests, one finds an increased white blood cell count. With non-blood derived cancers(ie. Brain, breast, colon, lung)there is no increase in the white blood cell count. This is why the routine blood test is not a good screening test for other cancers.