Histopathological Differences Between Idiopathic and Secondary Interstitial Pneumonia: An Elastic Fiber-Oriented Deep...

Area of Science:

• Pulmonary pathology
• Connective tissue research
• Digital pathology and AI

Background:

• Fibrotic interstitial lung diseases (ILDs) classification relies on histopathological patterns.
• Distinguishing idiopathic interstitial pneumonia (IIP) from secondary interstitial pneumonia (SIP) is diagnostically challenging.
• Multidisciplinary discussion is crucial for integrated ILD diagnosis.

Purpose of the Study:

• To investigate differences in collagen and elastic fiber composition between IIP and SIP.
• To utilize machine learning-based quantitative analysis for objective assessment.
• To explore the role of elastic fiber structural characteristics in ILD differential diagnosis.

Main Methods:

• Analysis of 780 Elastica van Gieson (EVG)-stained whole-slide images from 93 fibrotic ILD patients.
• Quantitative measurement of collagen and elastic fiber areas using HALO-AI.
• Identification and quantification of elastic fiber aggregation within fibrotic areas.

Main Results:

• No significant differences in collagen fiber area or total elastic fiber area between IIP and SIP.
• Significantly higher elastic fiber aggregation area/fibrosis area ratio in SIP compared to IIP, especially in lower lobes (P = 0.0010).
• Consistent findings across usual interstitial pneumonia and nonspecific interstitial pneumonia patterns, with SIP showing greater aggregation.

Conclusions:

• Secondary interstitial pneumonia (SIP) exhibits greater elastic fiber aggregation than idiopathic interstitial pneumonia (IIP).
• Quantitative assessment of elastic fiber quantity and structure aids in differential diagnosis of ILDs.
• Findings offer novel insights into the pathogenesis of fibrotic interstitial lung diseases.