The 2025 interstitial pneumonia classification marks a significant turning point in respiratory medicine and clinical pathology. Previously, global classifications focused heavily on idiopathic cases. However, the latest update from the ATS/ERS now integrates secondary causes, such as connective tissue diseases and environmental exposures. Consequently, pathologists must evaluate biopsies using a broader multidisciplinary lens to identify specific underlying triggers. This transition ensures that diagnostic frameworks remain practical and relevant for modern clinical settings. Moreover, clinicians can now apply these updated patterns to a much wider patient population than ever before.

Key Changes in the 2025 Interstitial Pneumonia Classification

The 2025 update introduces several vital changes designed to improve diagnostic accuracy and reporting consistency. Specifically, the framework subclassifies disorders into interstitial (fibrotic vs. non-fibrotic) and alveolar filling patterns. Additionally, the term "bronchiolocentric interstitial pneumonia" (BIP) replaces older, less specific descriptors for airway-centered diseases. Another notable change involves renaming Desquamative Interstitial Pneumonia (DIP) to Alveolar Macrophage Pneumonia (AMP). Furthermore, Acute Interstitial Pneumonia (AIP) is now formally termed Idiopathic Diffuse Alveolar Damage (IDAD). Therefore, these terminology updates better reflect the actual histogenesis and biological nature of lung injuries.

Applying Diagnostic Confidence in Clinical Practice

Under the new guidelines, pathologists must report diagnostic confidence levels in their biopsy evaluations. For instance, findings might be categorized as "confident," "provisional," or "unclassifiable." This standardized lexicon facilitates clearer communication within multidisciplinary teams. Although cryobiopsy is becoming increasingly common in India and globally, specialists must still acknowledge its limitations regarding sample size and orientation. Thus, a methodological approach remains essential for both clinical diagnosis and prospective research. Following these guidelines helps ensure patients receive targeted treatments based on specific fibrotic or inflammatory patterns.

Frequently Asked Questions

What are the new subclassifications for interstitial disorders?

The 2025 update divides interstitial disorders into fibrotic and non-fibrotic variants. This distinction helps clinicians determine whether to prioritize anti-fibrotic therapy or immunosuppressive anti-inflammatory treatments.

Why was the terminology for AIP and DIP changed?

Renaming AIP to Idiopathic Diffuse Alveolar Damage and DIP to Alveolar Macrophage Pneumonia provides a more accurate description of the underlying cellular pathology and historical histogenesis.

Disclaimer: This content is for informational and educational purposes only. It does not constitute medical advice or establish a doctor-patient relationship. Always consult a qualified healthcare professional regarding any medical condition or treatment. Refer to the latest local and national guidelines for clinical practice.

References

Nicholson AG et al. The 2025 ATS/ERS update of the international multidisciplinary classification of the interstitial pneumonias: implications for the pathologist. Histopathology. 2026 Jun 06. doi: 10.1111/his.70167. PMID: 42249728.

Ryerson CJ, Adegunsoye A, Piciucchi S, et al. Update of the international multidisciplinary classification of the interstitial pneumonias: an ERS/ATS statement. Eur Respir J. 2025;66(6). doi: 10.1183/13993003.00158-2025.

Kim KH, Song JW. 2025 ERS/ATS Update of the Classification of Interstitial Pneumonias: Key Changes. Korean J Med. 2026;101(1):13-20. doi: 10.3904/kjm.2026.101.1.13.