[1327] Utility of Multiplex Mutation Analysis in the Diagnosis of Chronic Myelomonocytic Leukemia

Daphne C Ang, Tibor Kovacsovics, Jennifer Dunlap, Nicky Leeborg, Marc Loriaux, Guang Fan. Oregon Health & Science University, Portland, OR

Background: Chronic myelomonocytic leukemia (CMML) is a myeloid neoplasm characterized by both myeloproliferative and myelodysplastic features. Clonal cytogenetic abnormalities are identified in only 20%-30% of CMML patients. It can be diagnostically challenging to rule out reactive monocytosis in some cases. Several gene mutations have recently been implicated in the pathogenesis of CMML and involve tyrosine kinase-signaling pathways, transcriptional regulation, metabolism, and epigenetic regulatory mechanisms. This study is designed to test for recurrent mutations and to determine the frequency of mutations in CMML using a multiplex mass spectrometry based approach.
Design: The Oregon Health and Science University (OHSU) surgical pathology database was searched from 2010-2012 to identify consecutive CMML cases fulfilling WHO diagnostic criteria. Standard cytogenetic karyotype analyses and molecular studies were performed on the diagnostic bone marrow specimen. DNA extracts were screened for point mutations using a multiplex PCR panel with mass-spectroscopy read out which covers 344 point mutations across 31 genes including ABL1, AKT1, AKT2, AKT3, BRAF, CBL, CBLB, FBXW7, FES, FGFR4, FLT3, FMS, GATA1, HRAS, IDH1, IDH2, JAK1, JAK2, KIT, KRAS, MET, MPL, NOTCH1, NPM1, NRAS, NTRK1, PAX5, PDGFRB, PTPN11, and SOS1.
Results: Thirty five out of 48 cases of CMML identified in the OHSU files had available cytogenetic studies. Only 11/35 cases (31%) had cytogenetic abnormalities: trisomy 8 (4), trisomy 21 (2), chromosome 7 abnormality (1), del 13q (1), complex karyotype (1), t(5;12)(1), and t(3;3)(1). 23 cases had available DNA for mutation screening which showed 12 cases (52%) have detectable mutations in the following genes: CBL (4), CKIT, JAK2, KRAS, NRAS (3), NPM, and PTPN11. Eight mutation positive cases had normal cytogenetics. Concomitant molecular and cytogenetic abnormalities were seen in 4 cases: 1 case with trisomy 8 and CBL C384Y, 1 case with trisomy 21 and JAK2 V617F, 1 case with t(5;12) with PTPN11 P491L and 1 case with derivative 7 and CKIT D816V.
Conclusions: Performing routine multiplex molecular testing in addition to cytogenetic studies in CMML patients increased detection of clonal abnormalities from 31% to 65%, with frequent CBL and NRAs mutations in our cohort. This study confirms that gene mutations are common events in CMML and multiplex mutation analysis can be applied in the clinical setting to assist in diagnosis and may identify actionable mutations for targeted therapy.
Category: Hematopathology

Monday, March 4, 2013 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 199, Monday Morning

 

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