Tazelaar, Henry D.

E-cigarette or vaping-associated lung injury (EVALI) was initially recognized as a public health problem in 2019, but pathologic changes from vaping (if any) outside the context of EVALI remain unknown. We aimed to further characterize the pathology of EVALI and vaping-associated changes in otherwise healthy patients without EVALI, including those presenting with spontaneous pneumothorax. Archives were searched for lung specimens from these patient groups (2019 to 2025). Previously reported cases were excluded. Clinical history and pathology slides were reviewed. Sixty-three patients (43 men; mean age: 36.0±15.2 y) were enrolled, including 47 wedge resections, 15 transbronchial biopsies, and 1 core biopsy. All reported current or recent vaping, and 24 reported prior or concurrent cigarette smoking. Thirty-six met criteria for EVALI and showed characteristic histologic features; novel findings included 12 (35%) with coarse lipid vacuolization and 6 (18%) with grungy proteinosis-like deposits. Eleven patients with prior suspected EVALI had chronic respiratory symptoms with airway-centered macrophages and variable airway-centered fibrosis. The remaining 16 patients presented with spontaneous pneumothoraces without EVALI and had rare foamy or lightly pigmented macrophages in airspaces but no other abnormalities beyond secondary changes from the pneumothorax. To our knowledge, this is the largest pathologic study of EVALI and the first to review histologic findings in the lungs of otherwise healthy vapers. EVALI is less common than in 2019 but is still encountered. Outside the context of EVALI, patients who vape and develop spontaneous pneumothorax have minimal histologic changes. The role (if any) of vaping in the development of pneumothorax remains unknown.

IgA vasculitis (IgAV) and IgA nephropathy (IgAN) are closely related disorders that usually present in childhood. Pulmonary involvement is rare and histopathologic features thereof in adults are poorly understood. Institutional archives were searched for adults with IgAV or IgAN and diffuse parenchymal lung disease. Ten patients (6 men, median age 59 years) with lung tissue sampling were enrolled. Clinical history and pathology slides were reviewed. All patients were diagnosed with IgAV or IgAN before or concurrently with lung disease. Symptoms were nonspecific but hemoptysis was common. Radiologically, bilateral ground-glass opacities, consolidation, and reticulonodular densities were typical. Histologically, 6 cases (60%) featured acute or subacute diffuse alveolar hemorrhage (DAH) accompanied by definite (40%) or probable (20%) capillaritis. Two cases (20%) featured resolved DAH only, manifesting as alveolar hemosiderosis without other changes. And 2 cases featured organizing pneumonia without DAH. Five patients had a chronic interstitial pneumonia in the background, including 3 with nonspecific interstitial pneumonia (NSIP) and 2 with unclassifiable fibrosis. Findings were similar in IgAV versus IgAN. Of 4 patients with follow-up information, 2 died during hospitalization, one died 9 weeks later of secondary complications, and one was treated with rituximab and nintedanib and is alive 2 years later. To our knowledge, this is the largest series detailing pulmonary histopathologic findings in adults with IgAV or IgAN. Most cases show acute DAH with capillaritis; less commonly, old DAH, organizing pneumonia, NSIP, or unclassifiable fibrosis may be observed. Some patients do well with treatment but fatal cases also occur.

Context.— Distinguishing benign from malignant processes in small lung biopsy specimens is challenging, particularly in the presence of architectural distortion and crush artifacts. Mimics include reactive type II pneumocytes in peribronchiolar metaplasia or organizing pneumonia and benign mucinous elements, including goblet cells and submucosal glands, which can mimic adenocarcinoma with mucinous features. Objective.— To understand whether caudal-type homeobox 2 (CDX2) and cytokeratin 20 (CK20) immunoreactivity is specific to malignant epithelial processes and evaluate their expression in a range of benign, premalignant, and malignant pulmonary lesions. Design.— We assessed CDX2 and CK20 immunohistochemistry in 48 cases of interstitial lung disease with reactive type II pneumocytes, 13 foci of atypical adenomatous hyperplasia, 11 bronchiolar adenomas, 4 adenocarcinomas in situ, 25 minimally invasive adenocarcinomas, 39 pulmonary adenocarcinomas with mucinous features, 6 mucoepidermoid carcinomas, and 1 squamous papilloma with goblet cell hyperplasia. Results.— No expression of CDX2 or CK20 was observed in reactive processes, goblet cells, bronchial glands, atypical adenomatous hyperplasia, or bronchiolar adenomas. In adenocarcinomas with mucinous features (n = 39), 9 (23%) were CK20-reactive and 8 (20%) were CDX2-reactive. A minority of nonmucinous and mucinous minimally invasive adenocarcinomas (n = 25) showed immunoreactivity (3 [12%] for each marker), while all in situ adenocarcinomas were negative. Conclusions.— Our findings demonstrate that CDX2 and CK20 are not expressed in benign or reactive type II pneumocytes and are specific for malignancy, particularly adenocarcinomas with mucinous features. Immunoreactivity with either marker in small biopsy specimens can support a diagnosis of malignancy, especially in morphologically equivocal or limited samples. Absence of staining does not exclude malignancy, but immunoreactivity with CDX2 and/or CK20 provides strong supportive evidence for a malignant process.

AimsPolymyalgia rheumatica (PMR) is a chronic autoimmune disorder that mainly affects older adults. Pulmonary disease in PMR is rare but may be under‐recognized and pathological descriptions thereof are few. We aimed to characterize diffuse parenchymal lung disease (DPLD) in PMR.Methods and resultsInstitutional archives were searched for patients having PMR and DPLD with lung tissue sampling. After excluding cases with infection, concomitant rheumatoid arthritis, or smoking‐related DPLD only, 11 patients (9 women, median age 75 years) were enrolled. Clinical history and pathology slides were reviewed. One of the 11 patients (9%) had concomitant giant cell arteritis; the remaining patients had no other rheumatological diseases. All had been treated for PMR with immunosuppression, and most presented years later (median 6 years) with non‐specific respiratory symptoms. Radiographically, bilateral ground‐glass opacities and reticulation were typical and were usually lower lobe predominant. Histologically, fibrosis was seen in 8 of 11 (73%) patients and was unclassifiable in four; non‐specific interstitial pneumonia was encountered in three patients, and usual interstitial pneumonia was seen in only one case. Evidence of acute lung injury occurred in 9 (82%) patients, including three with acute lung injury only, usually manifesting as organizing pneumonia. Diffuse alveolar haemorrhage was seen in four cases (29%), including two patients with haemoptysis and capillaritis.ConclusionsOur data corroborate prior reports of clinically significant DPLD in some patients with PMR. Histopathological findings mirror other rheumatological disorders and include diffuse alveolar haemorrhage with capillaritis. Additional studies are warranted to clarify the association between PMR and DPLD.

Transbronchial cryobiopsies (CB) are increasingly replacing surgical biopsies (video-assisted thoracoscopic/VATS biopsies) for diagnosing diffuse parenchymal lung disease (interstitial lung disease, ILD), but there is very little guidance for pathologists on CB interpretation. Here we propose a fairly simple approach. First, if the diagnosis can be made on a traditional forceps biopsy, it can be made on a cryobiopsy. Many diseases with specific features will fall into this category (eg, sarcoidosis or Langerhans cell histiocytosis). More problematic are patterns such as usual interstitial pneumonia (UIP) or nonspecific interstitial pneumonia (NSIP), in which low-power architecture is the key to diagnosis. In this circumstance, an adequate sample is crucial to look for features such as fibroblast foci, because a combination of fibroblast foci plus any patchy old fibrosis, fibrotic architectural remodeling, or honeycombing, allows a diagnosis of a UIP pattern. However, in most instances, CB will not separate the UIP patterns seen in idiopathic pulmonary fibrosis, fibrotic hypersensitivity pneumonitis, or connective tissue disease-interstitial lung disease (CTD-ILD), although giant cells/granulomas (uncommon findings) in this setting favor fibrotic hypersensitivity pneumonitis. Fibroblast foci can be difficult to differentiate from organizing pneumonia (OP), but granulation tissue plugs clearly in airspaces favor OP. Absent fibroblast foci, patchy old fibrosis, architectural distortion, and honeycombing by themselves do not allow a specific diagnosis. NSIP in CB microscopically looks like NSIP in VATS biopsies, and the presence of an NSIP or an NSIP+OP pattern is typical of CTD-ILD. All the above diagnoses require correlation with clinical and radiologic findings.

Diagnosing pulmonary rheumatoid nodules (RN) is challenging because they are rare and share clinical, radiologic, and histopathologic features with other necrotizing granulomatous diseases such as infectious granulomas (IG) and granulomatosis with polyangiitis (GPA). Herein, we revisit the histopathologic features of RN and the findings in the adjacent lung tissue, in comparison with IG and GPA, to identify distinguishing features. Twenty-eight cases with surgically resected RN evaluated at our institution (1991 to 2024), 33 IG (10 mycobacterial infection, 10 histoplasmosis, 13 coccidiomycosis), and 10 GPA cases were included in the study. All available slides with H&E and special stains were reviewed for various histologic parameters within the nodules and in surrounding lung tissue. Many histopathologic features of RN overlap with the necrotizing granulomas seen in infections and GPA. However, some findings in the adjacent lung tissue showed significant differences. The lack of airspace granulomas/non-necrotizing granuloma and the absence of necrotizing vasculitis in the setting of RN can help to differentiate between infection cases and GPA, respectively. Given their considerable overlap, correlation with clinical context, serologic and microbiologic studies, as well as careful evaluation of special stains is crucial in the diagnosis of RN.

Context.— A monthly pathology journal club has met for 24 years. It was established to help members stay apprised of the literature relevant to diagnostic pulmonary pathology. Objective.— To assess whether the journal club met its goal and to report on opportunities identified for improvement. Design.— To determine whether articles chosen for discussion as opposed to notation were more significant, Scopus citation indices for article types reviewed from January 2007 to November 2023 were compared. A survey of current faculty was undertaken to determine if the club was meeting expectations and to identify improvement opportunities. Results.— Articles from January 2007 to November 2023 included 858 discussed and 3385 noted. Mean (SD) citation count was 103.0 (409.80) for discussion and 64.9 (259.77) for notation articles ( P < .001). The citation count was noticeably right skewed, as articles with high citation counts inflated the mean. Members were mostly satisfied with the way the journal club was structured and managed. Members most valued the summary of the articles, followed by the live discussion. Opportunities for improvement included decreasing the number of journals scanned, decreasing detail in summaries, and using generative artificial intelligence (AI) to facilitate summary generation. A pilot using AI anecdotally reduced preparatory time, but the human-edited summary included more specific context, critical commentary, and enhanced take-home messages, providing a more nuanced analysis. Conclusions.— The journal club met its initial goal. Opportunities for improvement have been identified including the use of generative AI to facilitate article summarization.