Immunophenotyping and differential diagnosis of hairy cell leukemia

The cells of hairy cell leukemia and its variant form have a distinct immunophenotype that seems to correspond to that of a mature activated memory B cell. Although the two diseases have similarities in histology and membrane marker expression, such as the selected immunoglobulin heavy-chain expression and the reactivity with certain B-cell activation markers, there are differences in their clinical course, morphology, and immunophenotype. Immunophenotyping is an essential tool for the diagnosis of these two disorders, for monitoring and assessing response to therapy, and for distinguishing them from other B-cell malignancies.