SMAD2 and chronic rhinosinusitis with nasal polyps: Thus, the aim of this study was to assess the expression levels of Smad2, pSmad3, TGFβ1, and CNPase protein via immunohistochemistry in sinus epithelial tissues from patients with CRSwNP (n = 20), CRSsNP (n = 23), and non-CRS patients (n = 8).