Acute lymphocytic leukemia stages
A numbered staging system is used to describe most types of cancer and their spread throughout the body. Typically, the size of the tumor and the spread of the cancer are evaluated and a stage is assigned. For ALL, staging does not occur in this way because the disease originates within the bone marrow and usually does not form tumor masses. Because ALL will likely spread to other organs before it is detected, the staging method would need to take into account factors other than the spread to differentiate the stages.
Rather than using traditional staging methods, physicians often factor in the subtype of ALL and the patient's age. This usually involves cytologic tests, flow cytometry and other lab tests to identify the subtype of ALL.
ALL classification based on immunophenotype
Immunophenotyping is a way to classify ALL. It factors in the type of lymphocyte (T cell or B cell), as well as how mature the cells are.
B-cell ALL staging
B lymphocytes, or B cells, are produced in the bone marrow. They also mature there. B cells play a large role in humoral immune response and serve the principal functions of making antibodies against antigens and developing into memory B cells after they have been activated by antigen interaction.
- Early pre-B ALL: Approximately 10 percent of ALL cases
- Common ALL: Approximately 50 percent of cases
- Pre-B ALL: Approximately 10 percent of cases
- Mature B-cell ALL (Burkitt leukemia): Approximately 4 percent of cases
T-cell ALL staging
T lymphocytes, or T cells, leave the bone marrow before maturation and move to the thymus, where they mature. T cells play a central role in cell-mediated immunity. There are several different subsets of T cells that have distinct functions. The different subsets of T cells include Helper, Cytotoxic, Memory, Regulatory, Natural killer and Gamma Delta T cells.
- Pre-T ALL: Approximately 5 to 10 percent of cases
- Mature T-cell ALL: Approximately 15 to 20 percent of cases