De novo appearance of der(1;7)(q10;p10) is associated with leukemic transformation and unfavorable prognosis in essential thrombocythemia.

Leukemic transformation or myelofibrosis is a major concern in managing patients with chronic myeloproliferative disorders, including essential thrombocythemia (ET). We analyze the relationship between cytogenetic changes and the transformation in 89 patients with ET; 8 patients experienced transformation, including 2 patients with acute leukemia following myelofibrosis, 3 with acute leukemia, and 3 with myelofibrosis. Among the eight patients showing transformation, two patients developing myelofibrosis derived from a group with normal cytogenetics, but the remaining six were categorized as showing de novo appearance of cytogenetic changes. Two leukemia patients had de novo cytogenetic changes at the time of leukemia diagnosis, whereas two patients with acute leukemia following myelofibrosis showed der(1;7) during their myelofibrosis period. Moreover, patients with der(1;7) did not receive any cytotoxic agents before the appearance of der(1;7), indicating that detection of der(1;7) may have predictive value for not only leukemic transformation but also unfavorable prognosis.