ON THIS PAGE: You will learn about how doctors describe ALL. This is called subtype and classification. Use the menu to see other pages.
Doctors divide ALL into subtypes and classify the disease based on the type of lymphocytes that are affected. For example, flow cytometry (see Diagnosis) distinguishes between ALL involving T cells or B cells. Specific chromosomal or genetic changes in the cancer cells are used to help plan treatment and predict prognosis.
Precursor B-cell ALL
Precursor T-cell ALL
Philadelphia chromosome positive (BCR-ABL fusion) ALL (see below)
Some patients have a type of leukemia called biphenotypic acute leukemia, also called mixed phenotype acute leukemia or ambiguous lineage acute leukemia. This means that the disease has characteristics of both ALL and/or acute myeloid leukemia (AML). Often, the same treatments used for ALL are also used for this type of leukemia.
As described in Diagnosis, about 20% to 30% of adults with ALL have a genetic change or mutation called the Philadelphia chromosome (Ph). This causes 2 genes, BCR and ABL, to become 1 fusion gene called BCR-ABL.
The Philadelphia chromosome is found only in the cancerous blood-forming cells, not in other organs of the body. It is not inherited. Therefore, there is no concern about an increased risk of ALL for other family members.
The BCR-ABL gene causes specific types of white blood cells called B lymphoblasts to grow out of control. Knowing whether a person has the BCR-ABL gene helps the doctor predict a patient’s prognosis and recommend treatment. So, it is important to test for it.
About 20% to 25% of patients with precursor B-cell ALL have a type of ALL called Ph-like ALL. The genetic changes found in the leukemia cells of Ph-like ALL act like those linked with the Philadelphia chromosome. But, there are no signs of the Philadelphia chromosome in the leukemia cells. Instead, the leukemia cells have other mutations that act similarly. This means that the same types of treatments used for leukemia with the Philadelphia chromosome may also work for Ph-like ALL.
ALL classification and status of disease
In other types of cancer where a solid tumor forms, doctors agree on a set of stages that describe how big the tumor is and where it has spread. There is no formal staging system for ALL because it usually does not form a solid tumor. And it is often found throughout the body when diagnosed. Instead, there are general classifications used to describe ALL:
Newly diagnosed and untreated. The bone marrow contains abnormal lymphoblasts. The person may or may not have any symptoms. A patient often has decreased numbers of healthy white blood cells, red blood cells, and platelets. Some patients may have an overall increased number of white blood cells, but many of these may be abnormal lymphoblasts.
In remission. A patient has received treatment for ALL. The bone marrow contains less than 5% blasts, and the patient has no symptoms. The numbers of healthy white blood cells, red blood cells, and platelets are normal. New monitoring methods, called minimal residual disease (MRD; cancer cells not destroyed by treatment) methods, are better able to find small numbers of remaining blasts. MRD methods are now being used more often to determine remission.
Refractory. Refractory leukemia means that the disease has not responded to treatment.
Recurrent or relapsed ALL. Recurrent leukemia has come back after being in remission. If the leukemia does return, there will be another round of tests to learn about the extent of the recurrence. These tests and scans are often similar to those done at the time of the original diagnosis.
The subtype and classification of ALL will help the doctor recommend a specific treatment plan. The next section in this guide is Treatment Options. You may use the menu to choose a different section to read in this guide.