KIT and systemic mastocytosis: In this case, the patient presented with criteria for SM, including one major criterion with an infiltrate of tryptase and CD117 positive mast cells (15 mast cells in aggregates) detected in bone marrow and four minor criteria: 30% of the mast cells exhibited spindle-shaped morphology in bone marrow biopsy; presence of mast cells in spleen expressing CD25 and CD2, persistent elevated serum tryptase and the presence of the KIT D816V mutation.