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Clinicopathologic Features of IDH2 R172-Mutated Myeloid Neoplasms
Adam R Davis1, Briana C Canady2, Nidhi Aggarwal1,2
1Department of Pathology, UPMC, Pittsburgh, PA, USA.
Objectives:
IDH1 and IDH2 are among the most commonly mutated genes in myeloid neoplasms (MNs). It has been proposed that IDH2 R172 mutations (mR172) define a molecular subtype of acute myeloid leukemia (AML), but the clinicopathologic features of AML with mR172 have not been fully described.
Methods:
We retrospectively identified and characterized all mR172 MNs with increased blasts in our archive for comparison to a similar number of MNs with IDH2 R140 (mR140) and IDH1 R132 (mR132) mutations (n = 39).
Results:
mR172 cases had lower leukocyte counts and bone marrow cellularity than did non-mR172 cases. mR172 MNs often displayed blasts with highly invaginated, cleaved nuclei and typically expressed CD34, HLA-DR, CD117, and CD13 but often with diminished CD33. mR172 cases often had co-occurring mutations in myelodysplasia-associated genes and/or an adverse karyotype. Despite frequent adverse-risk genetic changes, in our cohort mR172 cases had significantly improved overall survival vs non-mR172 cases (P = .01), and we validated that mR172 was associated with improved survival in an independent large data set.
Conclusions:
We show that MNs with mR172 represent a morphologically and phenotypically distinct subtype, which in our cohort exhibited relatively favorable survival that is not captured in current AML risk assignment.
