BRAF V600E and MAP2K1 Mutations in Hairy Cell Leukemia and Splenic Marginal Zone Lymphoma Cases

Dear Editor, Differentiation of classic hairy cell leukemia (HCL-c) from HCLvariant (HCL-v) or splenic marginal zone lymphoma (SMZL) is important owing to their different treatment strategies and prognostic implications. Recently, testing for BRAF V600E mutations was suggested as an important diagnostic option for HCL-considering that it was exclusively detected in almost all cases [1]. The BRAF V600E mutation has been reported to be absent in most cases of immunoglobulin variable heavy chain rearrangements 4-34 (IGHV4-34)-positive HCL-c, HCL-v, and SMZL [2]. However, it was recently reported that high prevalence of MAP2K1 mutation is observed in IGHV-34-positive HCL-c (5/7, 71.4%) [3]. We investigated the presence of BRAF V600E and MAP2K1 mutations in four HCL-c, two HCL-v, and four SMZL cases involving the bone marrow that were diagnosed between June 2005 and June 2014 at our hospital. HCL and SMZL was diagnosed in accordance with the 2008 WHO classification of tumors of hematopoietic and lymphoid tissues [4]. HCL-c was defined as the expression of Annexin A1, CD20, CD22, CD11c, CD103, and CD25. HCL-v was defined as the negative expression of CD25 and Annexin A1 [4]. Real-time PCR was performed by using the Real Q BRAF V600E Detection Kits (BioSewoom Inc., Seoul, Korea) on the 7500 Fast Real-Time System (Applied Biosystems, Foster City, CA, USA), according to the manufacturer’s instructions [5]. Mutant enrichment 3 ́-modified oligonucleotide (MEMO)-PCR and sequencing analysis for the BRAF V600E mutation were performed as previously described [6]. We designed the sequencing primers for MAP2K: exon 2 (forward) 5 ́-TTCTCTGGTGACAGTATTGACTTG-3 ́, (reverse) 5 ́-CCCTGAGAAATAATCCAATTACĆ and exon 3 (forward) 5 ́-CATCCCTTCCTCCCTCTTTC-3 ́, (reverse) 5 ́-CTCTTAAGGCCATTGCTCCA-3 ́. Sequencing was performed by using the BigDye Terminator Cycle Sequencing Ready Reaction Kit on the ABI Prism 3130 Genetic Analyzer (Applied Biosystems). The DNA extracted from bone marrow aspirate slide was used for sequencing analysis. We detected the BRAF V600E mutation in all HCL-c cases ei-