What is Leukemia? Leukemia is a condition where the blood-forming tissues become cancerous including the lymphatic system and the bone marrow. In other words, it is the cancer of the blood cells. There are different types of leukemia, and some exist in children while others exist in adults. Leukemia is mostly common with the white blood cells, which are the infection fighters. Normally, these cells grow and divide in an orderly manner, as the body requires. However, with leukemia, the bone marr...