Pathologic and radiologic differences between idiopathic and collagen vascular disease-related usual interstitial pneumonia

Background: Patients with usual interstitial pneumonia (UIP) associated with collagen vascular disease (CVD) have been reported to have a better prognosis than those with idiopathic pulmonary fibrosis with a UIP pattern (IPF/UIP) seen on histology. The aim of this study was to evaluate the pathologic and radiologic differences between the two conditions and their relationship with clinical outcome. Methods: A retrospective review of 100 patients (CVD-UIP, 39 patients; IPF/UIP, 61 patients) with UIP pattern diagnosed by surgical lung biopsy at one tertiary referral center. Results: The median follow-up period was 34.4 months. The CVD-UIP group was younger, included more women and nonsmokers, and showed better survival than the IPF/UIP group. Pathologically, CVD-UIP patients had fewer fibroblastic foci and smaller honeycombing (HC) spaces with higher germinal centers and total inflammation scores than IPF/UIP patients. Radiologically, CVD-UIP patients had a lower emphysema score and more likely a nontypical UIP pattern without HC. The germinal centers score was the best distinguishing feature between CVD-UIP and IPF/UIP patients (odds ratio, 2.948; p = 0.001) and was marginally related to survival (p = 0.076). The HC score (hazard ratio [HR], 1.134; p < 0.001), total lung capacity (TLC) [HR, 0.932; p = 0.004], and age (HR, 1.052; p = 0.017) were significant predictors of survival in all patients with UIP histology, regardless of the presence of CVD. Among IPF/UIP patients, those with positive autoantibodies were pathologically more similar to CVD-UIP than to IPF/UIP without autoantibodies, despite no difference in survival between them. Conclusions: The germinal centers score was the best discriminative between CVD-UIP and IPF/UIP patients; it was of marginal prognostic significance. Age, TLC, and HC score were independent prognostic factors in all patients with UIP histology.