Proliferation of elastic fibers in idiopathic pulmonary fibrosis: A whole-slide image analysis and comparison with pleuroparenchymal fibroelastosis

Abstract

Background

We occasionally encounter patients with idiopathic pulmonary fibrosis (IPF) who have similar imaging patterns to pleuroparenchymal fibroelastosis (PPFE) in the upper lung fields but are not diagnosed as PPFE clinically. The clinicopathological features and intrapulmonary distribution of elastic fibers and collagen fibers in these patients have not been fully elucidated.

Methods

We retrospectively reviewed the medical records of patients with a clinical diagnosis of IPF and selected the consecutive patients who received autopsy or pneumonectomy for lung transplantation. Patients with histologically confirmed PPFE were also reviewed for a comparison. We quantified the collagen fibers and elastic fibers in each lobe as a percentage of the nonaerated lung area (collagen fiber score and elastic fiber score, respectively) in histological specimens using a whole-slide image analysis, and compared these scores between IPF and PPFE patients.

Results

In a total of 55 patients (IPF, 48; PPFE, 7), there were no significant differences in the collagen fiber scores between IPF and PPFE patients. The elastic fiber scores in the upper lobe in PPFE patients were significantly higher than those in IPF patients (23.5 versus 10.3, p = 0.005). Of note, however: in 12 of 48 patients with IPF, the elastic fiber scores of the upper lobes were above the first quartile of those in the PPFE patients.

Conclusions

IPF shows intense elastosis in the upper lobes occasionally, and such cases are histologically indistinguishable from PPFE. There seem to be histological borderline cases between PPFE and IPF.

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