POSTN and nasal cavity polyp: In this prospective controlled study, we investigated the tissue-level immunohistochemical effects of oral corticosteroids (OCSs) and topical steroids on the expression of periostin, eotaxin, interleukin-4 (IL-4), transforming growth factor-β (TGF-β), and tumor necrosis factor-α (TNF-α) in nasal polyp tissue.