Acute Lymphocytic Leukemia (ALL) is leukemia that affects lymphocytes, a type of white blood cell. It is not a single disease, but a group of related diseases. In the past, doctors divided ALL into the following three subtypes, based mainly on how the leukemia cells looked under the microscope:
L1. Most common in children
L2. Most common in adults
L3. Most aggressive type; also called Burkitt-type leukemia
Newer lab tests now allow doctors to divide ALL into more specific classifications, based on the type of lymphocyte the disease starts in and how mature the cells are.
Early Pre-B ALL
Mature B-cell ALL (Burkitt-type leukemia)
Mature T-cell ALL