Most Myeloid Neoplasms With Deletion of Chromosome 16q Are Distinct From Acute Myeloid Leukemia With Inv(16)(p13.1q22)A Bone Marrow Pathology Group Multicenter Study

Objectives: Isolated deletion of the long arm of chromosome 16 (del(16q)) is rare in myeloid neoplasms (MNs) and was historically considered a variant of inv(16)(p13.1q22) (inv(16)), a subtype of acute myeloid leukemia (AML) associated with CBFB-MYH11 rearrangement and favorable prognosis. This study aims to determine clinicopathologic characteristics of patients with isolated del(16q) in MNs in comparison to AMLs with isolated inv(16). Methods: Clinicopathologic features were retrospectively reviewed in 18 MNs with del(16q) and 34 AMLs with inv(16) patients from seven institutions. Results: MNs with del(16q) occurred in elderly patients, often as secondary MNs. Blood monocytes and marrow eosinophils were lower in del(16q) than inv(16). Deletion of CBFB but not CBFB-MYH11 rearrangement was confirmed by fluorescence in situ hybridization or reverse transcription polymerase chain reaction in 14 of 14 del(16q) patients. The median overall survival was shorter in del(16q) than in inv(16) patients (12 vs 94 months, log rank P=.0002). Conclusions: Myeloid neoplasms with isolated del(16q) with deletion of the CBFB but lacking CBFB-MYH11 rearrangement should not be considered a variant of the AML-defining inv(16).