CD38 and Nasal polyposis: By examining CD38 and CD117 (ckit) expression, a CD38 high, CD117 low (MC t), a CD38 low CD117 high population were identified, and a novel intermediate mast cell population expressing CD38 high CD117 high that is highly proliferative in CRSwNP and N-ERD. This suggests that local mast cell proliferation contributes to the elevated numbers of polarized mast cells observed in nasal polyps (30).