Extramedullary blast transformation in the central nervous system in idiopathic myelofibrosis.

Idiopathic myelofibrosis (IM) is a myeloproliferative syndrome characterized by anemia, fibrosis of the bone marrow, variable proliferation of megakaryocytes, myelocytic and erythrocytic precursors, and splenomegaly. Extramedullary hematopoiesis can develop in diverse areas. Unlike in chronic granulocytic leukemia, transformation to acute leukemia is uncommon in IM. Transformation to acute leukemia is usually accompanied by the findings of progressive increase in blasts in peripheral blood or bone marrow [1]. We have recently treated a patient with an unusual transition from IM to acute leukemia in whom leukemic transformation began in the central nervous system.