How many main types of leukemia are there?

Leukemia is the general term used to describe a number of malignant diseases where the blood-forming organs produce increased numbers of leucocytes. Leucocytes are the colorless cells in blood and lymph etc. and which are important in fighting disease. CHRONIC AND ACUTE: In broad terms, leukemia is classified according to how fast it progresses: * In Chronic leukemia the cells develop slowly and the patient's condition gradually deteriorates over the years. * In Acute leukemia the blood-forming cells reproduce and accumulate very rapidly. If not treated quickly, death can ensue within a few months. TYPES There are about a dozen or so different types of leukemia classified according to the specific type of white/clear blood cell that is multiplying abnormally.
Main cell types affected and the term used for leukemic conditions of those cells: * Bone marrow lymphocytes (immune system cells) > lymphocytic leukemia. [cancers of other lymphocyte cells which develop in lymph nodes, spleen and organs other than bone marrow, are called lymphomas. These types of cancerous cells behave differently from those described as lymphocytic leukemias] * If either the granulocytes (bacteria-destroying cells) or the monocytes (macrophage-forming cells, i.e. large white cells which engulf foreign matter) are affected > myelogenous, or myeloid, leukemia. There are four possible permutations of the above classifications, and are the most common types of leukemia:
# Acute Myelogenous Leukemia (AML) # Chronic Myelogenous Leukemia (CML) # Acute Lymphocytic Leukemia (ALL) # Chronic Lymphocytic Leukemia (CLL) SUB-TYPES Medical science then identifies further sub-types, according to cancerous cell characteristics/features. * AML: To represent eight sub-types of AML the French-American-British classification system uses symbols M0, M1, M2 etc * CML is sub-classified according to three phases of development, 'chronic', 'accelerated' and 'blast' phases. * ALL is identified by the source of the cell, e.g. from the bone-marrow source being called ALL (B-cell), thymus-sourced being ALL (T-cell) etc. And the appearance of the cell falls into one of three L (Lymphocoytic) types, known as L-1, L-2 or L-3. * CLL is classified by staging, i.e. the stage the cancer has reached, as determined by cell appearance. There can be three or five stages, depending on which classification system is used. MORE DETAIL
Chronic leukemias can be further differentiated. e.g hairy cell leukemia (HCL), prolymphocytic leukemia (PLL), T-cell chronic lymphocytic leukemia (T-CLL), and chronic myelomonocytic leukemia (CMML). Of course it is possible to further differentiate the type of leukemia by identifying the specific DNA displacement/malfunction that is causing a particular cell to be malignant and which is being perpetuated in cell development and reproduction. For more information see Related links below this box.