Acute Lymphoblastic Leukemia
Diagnosis

Acute lymphoblastic leukemia (ALL) is usually suspected when a test finds abnormal blood counts and leukemic cells, or blasts, appear in the blood. Then, the diagnosis is established by examination of the bone marrow via bone marrow aspiration and biopsy. ALL is diagnosed when the bone marrow aspirate and biopsy contains 20 percent or more immature cells called blasts, determined to be lymphoid in nature.

It's generally difficult to be certain of an ALL diagnosis simply by the appearance of cells under the microscope. Therefore, additional laboratory tests are normally needed.

One important test is immunophenotyping (also called flow cytometry), which determines whether the cells are lymphoid (ALL) rather than myeloid (AML), based on proteins expressed in the leukemia cells. Immunophenotyping also determines whether they are T or B lymphocytes. In addition, chromosome testing, called cytogenetics, is a critical part of the evaluation that helps determine the appropriate course of treatment.