We evaluate the haematopathologic features of systemic mastocytosis associated with acute myeloid leukaemia (SM-AML) and the prognostic role of c-KIT mutation. Total 11 patients were enrolled. Cytochemistry using toluidine blue and tryptase was positive, as was immunohistochemistry for CD117 and CD25 on clustered mast cells; however, CD2 was expressed in only nine cases. In 10 cases, RUNX1-RUNX1T1 fusion gene was detected, and one patient presented with a t(5;6)(q22;q23) translocation at diagnosis. The c-KIT mutation D816V was detected in six patients. Patients with c-KIT mutations had higher relapse and death rates than those without; 4/5 (80.0%) and 5/6 (83.3%) vs. 1/5 (20%) and 2/5 (40%), respectively. Overall survival was also significantly shorter in cases with, than those without, c-KIT mutations. To identify rare cases of SM-AML, which have a dismal prognosis, c-KIT mutation study and careful examination for the presence of clustered mast cell infiltration by immunochemistry should be performed.
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