Not all leukemias are the same. There are 4 main types of leukemia. Knowing the specific type helps doctors better predict each patient’s prognosis (outlook) and select the best treatment.
Acute leukemia versus chronic leukemia
The first factor in classifying a patient’s leukemia is whether most of the abnormal cells look like normal white blood cells (mature) or look more like stem cells (immature).
In acute leukemia, the bone marrow cells cannot mature properly. Immature leukemia cells continue to reproduce and build up. Without treatment, most patients with acute leukemia would live only a few months. Some types of acute leukemia respond well to treatment, and many patients can be cured. Other types of acute leukemia have a less favorable outlook.
In chronic leukemia, the cells can mature partly but not completely. These cells may look fairly normal but they are not. They generally do not fight infection as well as do normal white blood cells. And they survive longer, build up, and crowd out normal cells. Chronic leukemias tend to progress over a longer period of time, and most patients can live for many years. But chronic leukemias are generally harder to cure than acute leukemias.
Myeloid leukemia versus lymphocytic leukemia
The second factor in classifying leukemia is the type of bone marrow cells that are affected.
Leukemias that start in early forms of myeloid cells – white blood cells (other than lymphocytes), red blood cells, or platelet-making cells (megakaryocytes) – are myeloid leukemias (also known as myelocytic, myelogenous, or non-lymphocytic leukemias).
If the cancer starts in early forms of lymphocytes, it is called lymphocytic leukemia (also known as lymphoid or lymphoblastic leukemia). Lymphomas are also cancers that start in lymphocytes. But whereas lymphocytic leukemias develop from cells in the bone marrow, lymphomas develop from cells in lymph nodes or other organs.
By considering whether leukemias are acute or chronic and whether they are myeloid or lymphocytic, they can be divided into 4 main types.