Leukemia is a cancer of the blood and bone marrow where cancerous cells fill the bone marrow and prevent healthy blood cells from being made. There are four main types of leukemia - acute and chronic forms of both myeloid and lymphocytic leukemia. Symptoms can include easy bruising, night sweats, excessive bleeding, fatigue, nausea and swollen belly. Leukemia is diagnosed through blood tests, bone marrow aspiration and biopsy. Treatments include chemotherapy, radiation, stem cell transplants, and biological therapies.