3q26.2/EVI1 rearrangement is associated with poor prognosis in classical Philadelphia chromosome-negative myeloproliferative neoplasms.

Classical Philadelphia chromosome-negative myeloproliferative neoplasms are a group of closely related myeloid disorders with different histologic features and clinical presentations at an early stage, but all later develop into a similar fibrotic stage with variable risk of acute transformation. The significance of 3q26.2/EVI1 rearrangement has been well recognized in acute myeloid leukemia, myelodysplastic syndrome, and chronic myeloid leukemia. However, the clinical importance of 3q26.2/EVI1 rearrangement in classical Philadelphia chromosome-negative myeloproliferative neoplasms is unknown. Here we reported 15 patients with classical Philadelphia chromosome-negative myeloproliferative neoplasms showing 3q26.2 rearrangement, including inv(3)(q21q26.2) (n=6), t(3;21)(q26.2;q22)(n=4), t(3;3)(q21;q26.2)(n=3), inv(3)(q13.3q26.2)(n=1), and t(3;12)(q26.2;p13)(n=1). In addition to 3q26.2 rearrangement, 9 of 15 cases had other concurrent karyotypical abnormalities, including -7/7q- and -5/5q-. There were 8 men and 7 women with a median age of 59 years (range, 35-79 years) at initial diagnosis of myeloproliferative neoplasms: 8 patients had primary myelofibrosis, 4 had polycythemia vera, and 3 had essential thrombocythemia. JAK2 V617F mutation was detected in 8/14 patients, including 4/4 with polycythemia vera. The median interval from the initial diagnosis of myeloproliferative neoplasms to the detection of 3q26.2 rearrangement was 44 months (range, 1-219 months). At time of emergence of 3q26.2 rearrangement, 11 patients were in blast phase and 2 patients had increased blasts (6-19%). Dyspoiesis, predominantly in megakaryocytes, were detected in all patients with adequate specimens at time of 3q26.2 rearrangement. Following 3q26.2 rearrangement, 12 patients received chemotherapy, but none of them achieved complete remission. Of 14 patients with follow-up information, all died with a median overall survival time of only 3 months (range 0-14 months) after the emergence of 3q26.2 rearrangement. In summary, 3q26.2 rearrangement in classical Philadelphia chromosome-negative myeloproliferative neoplasms is associated with other concurrent cytogenetic abnormalities, a rapid disease progression and blast transformation, a poor response to chemotherapy and a dismal prognosis.