Efficacy of Annexin A1 Immunostaining in Bone Marrow for the Diagnosis of Hairy Cell Leukemia

ABSTRACT

Splenic B-cell lymphomas (SBCLs) show characteristically pronounced splenomegaly without significant lymphadenopathy. Distinguishing hairy cell leukemia (HCL) from other SBCLs (splenic marginal zone lymphoma [SMZL], variant HCL [v-HCL], and splenic diffuse red pulp small B-cell lymphoma [SDRPL]) is essential to determine suitable treatments and prognoses. With advances in diagnostic modalities and therapies, splenectomy is not commonly performed, and thus diagnosis of HCL must be based on the results obtained using blood and bone marrow samples. Annexin A1 is known as the most specific marker for HCL. There has yet been no report of the assessment of annexin A1 immunostaining from Korea. In this study we analyzed samples from 13 Korean patients with SBCLs (three HCL, three v-HCL, six SMZL, and one SDRPL) from May 2001 to December 2016. Immunohistochemical analyses for annexin A1 and CD20 were performed using bone marrow sections; molecular analyses for detection of the BRAF V600E mutation were also performed. All HCL patients showed positive results for annexin A1 immunostaining and the presence of the BRAF V600E mutation, and negative results for other SBCLs. Our results confirmed the high specificity of annexin A1 and the BRAF V600E mutation as HCL markers. Molecular analysis requires expensive equipment and substantial manpower. Annexin A1 is a better alternative as an HCL marker than the BRAF V600E mutation in terms of cost-effectiveness.