What is it?
What are the types of leukemia?
By the course it takes, blood cancer divides into acute and chronic. The type that moves quickly and produces clinical signs and symptoms within a short time is called acute; the type that progresses slowly and develops over many years is called chronic leukemia.
The cancer cells in acute leukemias are less mature than those in chronic leukemias: they multiply quickly and leave the bone marrow rapidly without functioning. These non-functioning cells are called blasts. As blasts multiply quickly in acute leukemia they take over the space needed by the other healthy cells in the marrow, which is why symptoms appear within a short time.
Both types divide again into two branches according to the kind of white blood cell involved. If the white blood cell is a myelocyte it is called myeloid leukemia; if it is a lymphocyte, lymphoblastic leukemia. Beyond these there are far rarer types such as juvenile myelomonocytic leukemia, chronic myelomonocytic leukemia, myelodysplastic syndrome, myeloproliferative diseases and hairy cell leukemia.
In adults, acute myeloid and chronic lymphocytic leukemia are the common forms. In children leukemia usually presents as myeloid and acute myeloid leukemia (AML). Acute leukemia is the term used for a bone marrow cancer characterised by leukocytes that never fully complete their development.
Leukemias are generally examined in four main subcategories.
Acute lymphoblastic leukemia (ALL)
ALL is a blood cancer caused by the uncontrolled multiplication of primitive white blood cells. It accounts for 80% of childhood leukemia patients and 20% of adults. The five-year survival rate is 68%.
Acute myeloid leukemia (AML)
AML arises from the uncontrolled multiplication of myelocytic blasts and makes up half of the leukemias seen in young people. It is the most common acute leukemia in adults. The five-year survival rate is 26%.
Chronic lymphocytic leukemia (CLL)
CLL occurs when white blood cells of lymphoid origin mature and then multiply uncontrollably. These cells are non-functioning, and CLL is usually seen between the ages of 60 and 70. The five-year survival rate is 83%.
Chronic myeloid leukemia (CML)
Seen in people between 25 and 60, CML arises from the multiplication of myeloid cells. The five-year survival rate for this type is 67%.