RUNX1 and systemic mastocytosis: In addition, only one case with an SF3B1 mutation tested positive for one or more mutations in SRSF2, ASXL1 and RUNX1 (S/A/R), known to be an adverse prognostic factor in advanced SM [38], whereas 10/14 cases in group 3 were S/A/R positive (P = 0.009; Fisher’s exact test).