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Nonneoplastic Lung Disease for the Surgical Pathologist

Belchis, Deborah MD

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doi: 10.1097/PCR.0000000000000179
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It is with great pleasure that I present this issue focused on nonneoplastic lung disease. As practicing pathologists, we often find nonneoplastic lung disease to be a diagnostic challenge. Lung biopsies are relatively infrequent for most of us, providing little opportunity to hone our skills. Inflammatory and fibrosing processes can obscure normal landmarks, making it hard to assess the diseased lung compartment. To compound the difficulty, the variety of nonneoplastic disorders shows significant morphologic overlap. Finally, even within the same diseased lung, morphologic features may vary from one area to another. In this issue, a group of distinguished pulmonary pathologists shares their expertise in diagnosing nonneoplastic diseases. The authors have tried to guide the pathologist’s focus, pointing out the salient features of each entity that lead to the correct diagnosis.

In the first article, Drs Khalil, Allen, and Kurdowska present a case of acute respiratory distress syndrome (ARDS) arising in the setting of cytomegalovirus infection in a human immunodeficiency virus–positive man. Acute respiratory distress syndrome is the prototypic example of acute lung injury. This article provides an excellent discussion of the current understanding of the pathogenesis of ARDS, the radiographic findings, and the diverse conditions that are associated with its development. The stages of diffuse alveolar damage (DAD)—the pathologic correlate of ARDS—are clearly illustrated and presented. Of particular interest is the fact that cytomegalovirus inclusions and the more diagnostic features of DAD were not present in the initial biopsy, which showed only organizing pneumonia. It was not until the autopsy that the full picture was made clear. This case clearly illustrates the limitations of the lung biopsy and also highlights the importance of the autopsy, even in the high-resolution computed tomography era.

The next article, by Drs Lagstein and Myers, again shows features of DAD but in a very different setting. In this instance, the patient suffers an acute exacerbation of usual interstitial pneumonia (UIP), as illustrated by the superimposition of DAD on the background changes of UIP. The histopathologic features of both entities are clearly and excellently illustrated. Usual interstitial pneumonia continues to be a challenging diagnosis in the field of pulmonary pathology. In their article, Drs Lagstein and Myers provide a clear discussion of the morphologic features required for the diagnosis of UIP. They then compare and contrast UIP with the other interstitial lung diseases with which UIP is most commonly confused. The familiarity of the authors with the areas most likely to cause confusion for the general surgical pathologist enables them to address each of these points in a clear concise manner, guiding the reader through potential pitfalls and providing clarification of confusing points. This is an article to have at your elbow as you sign out any lung biopsy in which UIP is in the differential.

The next article by Drs Elatra, Ma, and Koss is a comprehensive and scholarly review of sarcoidosis, covering both the pulmonary and systemic pathologic features and presentations, the role of bronchioloalveolar lavage for diagnosis, and the role of lung transplantation. The article provides an excellent discussion of necrotizing sarcoid, a diagnosis that causes confusion among pathologists and nonpathologists. And last but not at all least, the authors provide an authoritative and comprehensive discussion of the differential diagnosis of granulomatous inflammation in the lung.

Interstitial lung disease is a well-recognized complication of connective tissue diseases. Drs Shyu, Oliveira, Jaco, Tavora, and Burke discuss interstitial lung disease arising in the setting of anti-Ro/SSA autoantibodies. In both of these cases, the pulmonary disease defined the patients’ clinical courses. Capillaritis can be a difficult diagnosis to make because of its patchy distribution and the obscuring foci of organizing pneumonia that may be present, as clearly illustrated in the first patient. As indicated by the authors, the pulmonary disease may precede the diagnosis of the connective tissue disease, highlighting the important role played by the pathologist in this situation.

The next article presents a case of plexiform pulmonary hypertension. Vascular changes of the lung can be difficult to identify. In this beautifully illustrated article, Drs Burke and Tavora highlight the findings in plexiform lesions. The article begins with a case report of a young woman who is found to have idiopathic pulmonary hypertension. The case is a perfect segue into the discussion of pulmonary arterial hypertension from the clinical workup, clinical presentation and subsequent complications, therapeutic intervention, and pathologic findings. They discuss the use of embolism to treat some of these cases, with photographs depicting the embolic material on histological sections. The classification of pulmonary hypertension has changed over the years, and this is also discussed with a table outlining the different categories.

The next article by Drs Smith, Gotway, Larsen, Colby, Tazelaar, and Leslie is a comprehensive and thorough review of diffuse cystic pulmonary lung disease. Diffuse cystic lung disease includes a diverse group of disorders ranging from inherited disorders such as Birt-Hogg-Dubé syndrome, to smoking-associated malignancies such as pulmonary Langerhans cell histiocytosis, to lymphangioleiomyomatosis, which is now recognized to be a low-grade malignancy. The authors take a surgical pathology approach with detailed descriptions of the distinctive pathologic features of the cysts and correlate these with clinical and radiographic findings. Careful attention is paid to the use of ancillary tests to aid in the diagnosis. In addition to discussing those entities in which cystic lesions are a well-recognized component of the disease, the article also discusses situations in which cystic disease may be an unusual finding. For example, subacute hypersensitivity pneumonitis, amyloidosis, and metastatic cancer may be associated with cystic changes. The discussion is very complete and makes this article an important referral source for all practicing pathologists.

The last article by Dr Belchis discusses an approach to bronchiolar disorders. The article starts by defining small airways. This review divides bronchiolar disorders into pathologic categories with morphologic clues to the differential diagnosis and clinical and radiographic correlates.

It is my hope that this issue will be a valuable resource for the general surgical pathologist. Lung biopsies are sporadic specimens for the majority of us, making it difficult to develop a sense of comfort with these cases. I am hoping these articles will provide a guide and useful framework for evaluating lung biopsies in everyday pathology practice.

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