Hidden in Plain Sight: Incidental Interstitial Lung Disease and Its Progression on Routine Chest CT

Interstitial lung diseases (ILD) are characterized by inflammation, fibrosis, or both within the pulmonary interstitium, ultimately leading to respiratory failure. Recently, the nomenclature for these conditions has evolved, shifting toward descriptive radiological and pathological classifications rather than etiology-based naming, as highlighted in the 2025 guidelines. While effective therapies were unavailable for decades, the therapeutic landscape has transformed over the last ten years. Today, two mainstay medications are utilized to slow disease progression and more are on the horizon.

Given the availability of effective treatment, general radiologists face a growing responsibility to not only characterize ILD but, crucially, to detect it early when encountered incidentally on routine imaging. Recognizing disease progression is equally vital, as it directly impacts management. This lecture aims to demystify the complex classification of ILDs, emphasizing their clinical significance in daily practice. We will focus particularly on managing incidental ILD findings during initial cancer staging and routine follow-up scans—scenarios most frequently encountered by non-chest radiologists.