Fibroblastic foci in usual interstitial pneumonia: Idiopathic vs collagen vascular disease

A histologic feature of usual interstitial pneumonia is the presence of fibroblastic foci. As some patients with usual interstitial pneumonia and an underlying collagen vascular disease have a better prognosis we hypothesized that they would have fewer fibroblastic foci. Pathologists reviewed surgical lung biopsies from 108 patients with usual interstitial pneumonia (nine with collagen vascular disease) and assigned a score (absent 0, mild 1, moderate 2, marked 3) for fibroblastic foci. Patients with idiopathic usual interstitial pneumonia had a higher median profusion of fibroblastic foci (1.75 vs 1.0; p=0.003). Baseline characteristics were similar although patients with a collagen vascular disease were younger, had a shorter duration of symptoms, and higher percent predicted total lung capacity. Profusion of fibroblastic foci was the most discriminative feature for separating idiopathic from collagen vascular disease associated usual interstitial pneumonia, odds ratio 8.31 (95% confidence interval 1.98, 59.42; p=0.002) for a one unit increase in fibroblastic foci score. No deaths were noted in the collagen vascular disease associated UIP group; 52 deaths occurred in the idiopathic usual interstitial pneumonia group (log rank; p=0.005). We conclude that patients with collagen vascular disease associated usual interstitial pneumonia have fewer fibroblastic foci and improved survival.