Kaplan-Meier plots of the time to large splenomegaly development, time to splenectomy, and time to leukemic transformation in JAK2 V617F-negative and JAK2 V617F-positive groups. (A) The time to large splenomegaly development is shown in the population selected for outcome analysis (a total of 174 patients) for patients who were JAK2 V617F negative or JAK2 V617F positive at the diagnosis. (B) The time to splenectomy in both groups is shown. (C) The time to leukemic transformation in both groups is shown. P values for all analyses are from log-rank tests. ---- indicates JAK2 V617F-positive; —, JAK2 V617F-negative.