Nonspecific interstitial pneumonia and usual interstitial pneumonia: is differentiation possible by high-resolution computed tomography?

Nonspecific interstitial pneumonia (NSIP) is a form of idiopathic interstitial pneumonia characterized histologically by varying degrees of interstitial inflammation and fibrosis that are temporally and morphologically homogeneous in comparison with usual interstitial pneumonia (UIP). Differentiation from UIP is very important because treatment and prognosis are different between NSIP and UIP. Although there are limitations for the differentiation between NSIP and UIP on computed tomography, some computed tomography findings contribute to it. Relatively peribronchovascular distribution, wide extent of areas with ground-glass attenuation, and subpleural sparing are more highly seen in patients with NSIP, whereas wide extent of honeycombing and subpleural distribution are more common characteristics in patients with UIP.