Myeloid neoplasm with t(3;8)(q26;q24): report of six cases and review of the literature

3q26.2/MECOM Rearrangements by Pericentric Inv(3): Diagnostic Challenges and Clinicopathologic Features

MECOM rearrangement (MECOM-R) resulting from 3q26.2 aberrations is often associated with myeloid neoplasms and inferior prognosis in affected patients. Uncommonly, certain 3q26.2/MECOM-R can be subtle/cryptic and consequently overlooked by karyotyping. We identified 17 acute myeloid leukemia (AML) patients (male/female: 13/4 with a median age of 67 years, range 42 to 85 years) with a pericentric inv(3) leading to MECOM-R, with breakpoints at 3p23 (n = 11), 3p25 (n = 3), 3p21 (n = 2) and 3p13 (n = 1) on 3p and 3q26.2 on 3q. These pericentric inv(3)s were overlooked by karyotyping initially in 16 of 17 cases and later detected by metaphase FISH analysis. Similar to the patients with classic/paracentric inv(3)(q21q26.2), patients with pericentric inv(3) exhibited frequent cytopenia, morphological dysplasia (especially megakaryocytes), -7/del(7q), frequent NRAS (n = 6), RUNX1 (n = 5) and FLT-3 (n = 4) mutations and dismal outcomes (median overall survival: 14 months). However, patients with pericentric inv(3) more frequently had AML with thrombocytopenia (n = 15, 88%), relative monocytosis in peripheral blood (n = 15, 88%), decreased megakaryocytes (n = 11, 65%), and lower SF3B1 mutation. We conclude that AML with pericentric inv(3) shares some similarities with AML associated with classic/paracentric inv(3)/GATA2::MECOM but also shows certain unique features. Pericentric inv(3)s are often subtle/cryptic by chromosomal analysis. A reflex FISH analysis for MECOM-R is recommended in myeloid neoplasms showing -7/del(7q).

MECOM rearrangement involving the MYC locus: Two additional patients with the rare translocation, t(3;8)(q26.2;q24), and molecular review

A relatively small subset of myeloid neoplasms involve rearrangements of cytoband 3q26.2. Such rearrangements are often in response to therapy and carry a poor prognosis. The ectopic expression of MECOM is the result of such translocations. To date, thirty-three t(3;8)(q26.2;q24) cases have been reported; we contribute two patients with confirmed MECOM and MYC rearrangements. Both patients presented with pancytopenia and were diagnosed with myelodysplastic/myeloproliferative disorders. In addition to translocation t(3;8), Patient 1 possessed a derivative chromosome 5, while Patient 2 possessed monosomy 7; neither patient's clonal abnormalities resolved in follow-up studies. Of the previous 33 cases, one exhibited 5q loss, while monosomy 7 was found in fifteen. These findings contribute to the small number of reported cases with t(3;8) translocations. We also speculate about the molecular mechanisms associated with this translocation.