Diagnosis of Hypersensitivity Pneumonitis: Review and Summary of American College of Chest Physicians Statement. (10th April 2022)

• Record Type: Journal Article
• Authors: Yang, Soo-Ryum; Beasley, Mary B.; Churg, Andrew; Colby, Thomas V.; Fernández Pérez, Evans R.; Lynch, David; Müller, Nestor L.; Travis, William D.
• Is Part Of: American journal of surgical pathology. Volume 46:Number 4(2022)
• Page Start: e71
• Page End: e93
• Publication Date: 2022-04-10
• Subjects: hypersensitivity pneumonitis -- usual interstitial pneumonia -- nonspecific interstitial pneumonia -- lung -- computed tomography; Pathology, Surgical -- Periodicals; 617.0705
• DOI: 10.1097/PAS.0000000000001827
• Languages: English
• ISSNs: 0147-5185

Abstract

Abstract : Assessment of lung biopsies for the diagnosis of hypersensitivity pneumonitis (HP) is one of the most difficult diagnostic problems for surgical pathologists. It is a form of interstitial lung disease resulting from an immune reaction provoked by an inhaled antigen in susceptible individuals. Although this definition sounds simple, in practice, the diagnosis of HP can be challenging. To address these issues, the American College of Chest Physicians (CHEST) has recently published a guideline for the diagnosis of HP. In this review, we will explore the multidisciplinary diagnostic evaluation of HP with a focus on the pathologic features as outlined in the CHEST guidelines. The histologic criteria are divided into 4 diagnostic categories: (1) Typical nonfibrotic HP or fibrotic HP; (2) Compatible with nonfibrotic HP or fibrotic HP; (3) Indeterminate for nonfibrotic or fibrotic HP; and (4) Alternative Diagnosis. It is important to emphasize that patterns 1 to 3 do not represent discrete histologic entities or pathologic diagnoses. Rather, these categories are meant to serve as a practical guide for organizing a complex set of overlapping histologic patterns into an integrated diagnostic framework for facilitating multidisciplinary discussion. High-resolution computed tomography features are also summarized, emphasizing how the correlation of lung biopsies with computed tomography findings can help to favor the diagnosis, particularly in cases where biopsies are not typical for HP. This review highlights details of the histologic spectrum of HP as well as the utility of different types of biopsies and bronchoalveolar lavage. We also emphasize the importance of multidisciplinary discussion and the complex differential diagnosis.