Clustered Cystic Changes in Long-Term Follow-Up Thin-Section Computed Tomographic Findings in Fibrotic Nonspecific Interstitial Pneumonia

Objectives. The purpose of this study was to retrospectively assess cystic changes in findings on follow-up CT scans of patients with fibrotic nonspecific interstitial pneumonia (NSIP). Methods. The initial and last high-resolution CT scans of 58 patients with pathologically proven fibrotic NSIP were evaluated retrospectively. The median follow-up periods were 48 months (range, 12-183 months). The pattern, extent, and distribution of abnormal CT findings were compared with findings in the same region on previous and subsequent CT scans with a focus on cystic lesions. Results. Cystic lesions in a cluster were shown in 16 patients (28%) with fibrotic NSIP on the last CT scans. Focal clustered cysts were found in 5 cases and diffuse clustered cysts were seen in 11 cases. Focal clustered cysts mimicked honeycombing seen in usual interstitial pneumonia (UIP). Diffuse cysts were uniform in size in 7 of the 11 cases. Traction bronchiectasis in a cluster was seen in 3 of the 7 cases. The clustered cystic changes on CT during the course of NSIP mainly consisted of traction bronchiectasis and bronchiolectasis. Conclusions. Long-standing NSIP did not form honeycombing. The clustered cysts in patients with fibrotic NSIP were mainly remodeling of bronchiectasis.