Non-specific interstitial pneumonia (NSIP) is a form of idiopathic interstitial pneumonia.
Patients with an NSIP histologic pattern on biopsy have a better prognosis than those with usual interstitial pneumonia (UIP). There are two variants of NSIP: cellular and fibrosing. The cellular variant features chronic inflammatory cells with minimal collagen deposition while the fibrosing pattern consists of diffuse interstitial fibrosis with fewer inflammatory cells. In contrast to UIP, NSIP has little or no honeycomb change, and fibroblast foci are scant or absent.