# Comprehensive radiologic-pathologic correlation in systemic sclerosis-associated interstitial lung disease: identification of an early-stage CT findings

## TL;DR

This study identifies early CT findings in systemic sclerosis-associated lung disease, linking subtle imaging features to underlying fibrosis patterns.

## Contribution

The study introduces FANO as a novel CT finding associated with early-stage fibrotic changes in systemic sclerosis-associated interstitial lung disease.

## Key findings

- FANO was observed in 64% of patients and corresponded to perivenular fibrosis and peribronchiolar metaplasia.
- Irregular reticulation with traction bronchiolectasis indicated dense fibrosis and severe architectural destruction.
- Longitudinal follow-up showed FANO progressing to reticulation in many cases, suggesting early-stage detection potential.

## Abstract

To perform comprehensive radiological-pathological correlation in systemic sclerosis-associated interstitial lung disease (SSc-ILD) and identify characteristic findings, including subtle abnormalities potentially representing early-stage CT findings.

This retrospective study included 28 SSc-ILD patients who underwent surgical lung biopsy between July 2008 and July 2018. Two chest radiologists independently reviewed whole-lung high-resolution CT (HRCT) images, with the other two radiologists evaluating biopsy sites. Faint amorphous nodular opacity (FANO) was defined as a small, faint nodular opacity superimposed on amorphous ground-glass opacity (GGO) within 1 cm of the pleural surface, showing a band-like distribution parallel to the pleura. Three pulmonary pathologists performed histological evaluation. Discrepancies were resolved through consensus, with CT-pathologic correlation established through joint radiologist-pathologist review.

Twenty-eight patients (mean age, 57 years ± 10; 15 men) were evaluated with 79 biopsy specimens. Nonspecific interstitial pneumonia was the predominant pattern on whole-lung HRCT (21 patients, 75%) and pathology (17 patients, 61%). At biopsy sites, GGO was most frequent (92%), followed by reticulation (84%). Reticulation was accompanied by GGO in nearly all cases, reflecting underlying diffuse fibrotic changes. Reticulation patterns with or without traction bronchiolectasis corresponded to varying fibrosis types, spatial distribution, and architectural destruction severity. Specifically, irregular reticulation with traction bronchiolectasis indicated dense fibrosis with severe destruction, representing UIP-like features. FANO was observed in 18 patients (64%), predominantly in anterolateral upper lobes, and corresponded pathologically to perivenular fibrosis and peribronchiolar metaplasia with or without mucostasis. Longitudinal evaluation (median 32.5 months) in 14 patients showed progression in 71%; half of these showed coalescence into subpleural curvilinear opacities with reticulation.

SSc-ILD demonstrates predominantly diffuse fibrotic changes. Irregular reticulation with traction bronchiolectasis indicates UIP-like features, potentially identifying patients at risk for progression. FANO, observed most commonly in anterolateral upper lobes, frequently progresses to reticulation on longitudinal follow-up, suggesting potential value for early-stage detection.

SSc-ILD demonstrated diffuse fibrotic changes as a characteristic feature, while irregular reticulation with traction bronchiolectasis indicated UIP-like fibrosis with severe architectural destruction. FANO, a newly described finding observed in 64% of cases, was predominantly in anterolateral upper lobes and corresponded to perivenular fibrosis and peribronchiolar metaplasia, representing potential early-stage changes.

The online version contains supplementary material available at 10.1007/s11604-025-01922-2.