Translocation t(1;9) is a recurrent cytogenetic abnormality associated with progression of essential thrombocythemia patients displaying the JAK2 V617F mutation.

A cohort of 338 patients diagnosed with myeloproliferative neoplasms was investigated by conventional cytogenetics and evaluated for the presence of the JAK2 V617F mutation. A t(1;9)(p10;q10) in addition to two extra der(1;9)(q10;p10) chromosomes was observed in two patients of essential thrombocythemia that transformed to acute myelogenous leukemia or to myelofibrosis. These findings suggest that the presence of extra derivative chromosomes der(1q;9p) in combination with the JAK2 V617F mutation may play a role in the progression of myeloproliferative neoplasms and supports the use of cytogenetics in the follow-up of the disease. Published by Elsevier Ltd.