Italian researchers have reported that gene expression profiling can accurately identify hairy cell leukemia from other B-cell malignancies.  The details of this report appeared in the June 5, 2004 issue of TheLancet .

Hairy cell leukemia is a relatively rare, chronic B-cell lymphoproliferative disorder that responds to multiple therapies. However, few if any patients are cured. Hairy cells are made up of activated B-cells that co-express CD11c, CD19, CD20, CD22, CD25, and CD103. This is usually an indolent disease with neutropenia, anemia, thrombocytopenia, symptomatic splenomegaly, and constitutional symptoms. Patients are usually treated initially with cladribine (2-CdA, Leustatin®) which results in reported relapse-free survivals of 70-80% at 4-5 years. However, other treatments such as pentostatin (deoxycoformycin, Nipent®), interferon-alpha, splenectomy, and Rituxan® are also effective. 

Hairy cell leukemia can be confused with other B-cell malignancies that cause splenomegaly and researchers have been looking at more specific diagnostic tests.  In the current study, researchers looked at gene expression profiling of annexin A1 which is a gene that is “upregulated in hairy cell leukaemia.”  In this study they found that all 62 cases of hairy cell leukemia expressed annexin A1.  Annexin A1 was not expressed in over 250 samples from patients with variant hairy cell leukemia, chronic lymphocytic leukemia, prolymphocytic leukemia, splenic marginal zone lymphoma, nodal marginal zone lymphoma, follicular lymphoma, mantle cell lymphoma, diffuse large B-cell lymphoma, Burkett lymphoma and myeloma. These authors proposed that this simple, low cost test be included in the diagnostic analysis in patients thought to have hairy cell leukemia.  They also suggest that prospective trials be performed to confirm these findings.

Comments: This study shows the power of gene profiling to identify a specific disease category.  This test should take the confusion out of classification of hairy cell leukemia but more importantly it shows the way for future studies to more accurately classify patients with diseases that superficially look alike but behave differently.

Reference: Brunagelo F, Tiacci E, Liso A, et al. Simple Diagnostic Assay for Hairy Cell Leukaemia by Immunochemical Detection of Annexin A1 (ANXA1). Lancet 2004;363:1869-1870.