Larsen, Brandon T.

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.

Abstract Introduction Drug-induced pneumonitis is an important mimic of disseminated infection in immunocompromised hosts. Lenalidomide, an immunomodulatory agent widely used in multiple myeloma, has been associated with organizing and eosinophilic pneumonitis, and occasionally sarcoid-like granulomatous inflammation. The coexistence of acute fibrinous injury and granulomatous inflammation is exceptionally rare. We present a case of lenalidomide-associated acute fibrinous and granulomatous pneumonitis presenting with a miliary pattern following autologous stem cell transplant. Case Presentation A 44-year-old woman with kappa light-chain multiple myeloma, chronic kidney disease stage V, presented with 10 days of fever (to 105 °F), dry cough, hemoptysis, dyspnea and hypoxia requiring high flow oxygen. She had been on maintenance therapy with lenalidomide, daratumumab, and weekly dexamethasone after undergoing an autologous stem cell transplant for multiple myeloma, last administered one week before symptom onset.. CT chest (Figure 1-1) showed innumerable randomly distributed micronodules with ground-glass opacities and septal thickening, suggesting disseminated infection. Laboratory results revealed eosinophilia (950/µL), neutropenia, and profound hypogammaglobulinemia. Empiric piperacillin-tazobactam, doxycycline, and fluconazole were started for possible bacterial and/or fungal infection (history of positive Coccidioides IgM). Two bronchoscopies demonstrated multifocal hypervascular airway lesions. BAL differential showed 15 % eosinophils and > 30 % lymphocytes; cultures, Fungitell, and comprehensive testing for bacterial, fungal, mycobacterial, viral, and parasitic pathogens were negative. Cryobiopsy revealed acute fibrinous and granulomatous pneumonitis with negative GMS and acid-fast stains. Following withdrawal of lenalidomide and daratumumab, the patient’s symptoms and CT findings improved without further antimicrobial therapy within the same hospitalization (Figure 1-2). She received an 8-week prednisone taper with inhaled pentamidine prophylaxis. Follow-up CT showed complete clinical and radiographic resolution (Figure 1-3), confirming a grade 3 drug-induced pneumonitis. A bronchoscopy will be repeated to assess the endobronchial vascular lesions. Discussion Lenalidomide related lung injury typically manifests as organizing or eosinophilic pneumonitis. The presence of both fibrinous and granulomatous inflammation suggests a mixed hypersensitivity and immune-complex reaction possibly potentiated by immune reconstitution after autologous transplant. The miliary pattern and BAL eosinophilia closely mimic disseminated fungal or mycobacterial infection. A Naranjo Adverse Drug Reaction Probability Scale score of 7 supported a highly probable causal relationship. Awareness of this pattern is essential, as prompt drug cessation and corticosteroid therapy are curative and prevent progression to fibrotic lung injury. This abstract is funded by: None

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.

Ameloblastomas are locally aggressive odontogenic tumors that most commonly arise in the mandible and maxilla and often harbor BRAF V600E mutations. While rare extragnathic ameloblastomas have been reported, primary pulmonary cases have not been documented. We identified 3 pulmonary neoplasms with features of ameloblastoma that were submitted for consultation between 2022 and 2025 at 3 academic institutions and performed detailed clinicopathologic and molecular analysis. The tumors presented as 5.4 to 7.3 cm peribronchial solitary lung masses. All resected tumors exhibited a predominant stellate reticulum-like component composed of loosely arranged p40-reactive bland squamoid-to-spindled cells with long intercellular bridges, and streaming and swirling architecture, surrounded by palisaded columnar cells with focal reverse nuclear polarity at the interface with myxoid stroma. All tumors were immunoreactive for BRAF V600E IHC, and BRAF V600E mutations were confirmed by molecular assays, including broad next-generation sequencing on 2 cases. Florid hyperplasia of entrapped pneumocytes initially suggested a biphasic neoplasm, but the absence of BRAF V600E IHC labeling confirmed pneumocyte entrapment. Occult gnathic primary tumors were excluded by subsequent clinical examination, including negative panoramic dental x-rays. No recurrences or metastases have been observed to date. This first series of primary pulmonary ameloblastomas highlights a distinctive tumor with histologic and molecular features identical to gnathic counterparts. We discuss the potential histogenesis of these unusual tumors.

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.

ABSTRACT Background As Coccidioides spp. are endemic in the southwestern United States, awareness of the risk factors for severe disease and dissemination is important to avoid delays in diagnosis and treatment. In addition to immunocompetent patients, individuals of certain ethnic backgrounds, especially African and Filipino ancestry, are at higher risk for dissemination. Diagnostic testing may be complicated by the lack of available invasive specimens for histopathologic examination and culture. Case Summary A 29-year-old African American woman presented with a 6-year history of abdominal bloating and discomfort, which was previously diagnosed as endometriosis and possible irritable bowel syndrome. After multiple visits to primary care, urgent care, and emergency settings, she was referred for outpatient gynecology and gastrointestinal follow-up. Imaging revealed diffuse peritoneal nodules potentially concerning for malignancy, and biopsies revealed Coccidioides spp. spherules on the frozen section. Routine bacterial and fungal cultures from the biopsied nodules grew Coccidioides immitis/posadasii . The patient was placed on fluconazole with rapid symptom resolution and was maintained on fluconazole at a 2-year follow-up. Conclusion The case presented highlights a reasonably common occurrence in endemic regions—the delayed diagnosis of coccidioidomycosis due to the lack of consideration as the etiology of the patient’s symptoms. This patient was at risk for dissemination due to her ethnicity, and while the differential for her presenting symptoms was broad, coccidioidomycosis should have been considered. In immunocompetent patients, like the case presented, serologic testing should be pursued, as severe or disseminated cases typically have positive IgG responses.

Primary pulmonary myxoid sarcoma (PPMS) and thoracic angiomatoid fibrous histiocytoma (AFH) are rare neoplasms with EWSR1 fusions and overlapping morphology. Both tumor types often show epithelial membrane antigen expression, but AFH characteristically co-expresses desmin. We encountered a case of PPMS with the unexpected finding of patchy, strong anaplastic lymphoma kinase (ALK) (previously reported in AFH) and synaptophysin expression. We evaluated a cohort of PPMS and thoracic AFH with systematic morphologic comparison and surveyed for aberrant expression of ALK and synaptophysin. Medical records and slides were reviewed for 16 molecularly confirmed cases of PPMS (n=5) and thoracic AFH (n=11). Each case was scored for morphologic characteristics typical of PPMS and/or AFH. ALK, synaptophysin, chromogranin, desmin, and epithelial membrane antigen immunostains were performed on cases with available tissue. AFH and PPMS cases showed similar age at presentation and long-term tumor behavior. Almost all cases of PPMS and AFH had a fibrous pseudocapsule and lymphoid rim. All PPMS had myxoid stroma and reticular growth pattern, but these features were also present in a subset of AFH. Synaptophysin expression was present in 6 of 11 AFH and 1 of 5 PPMS; all tested cases were negative for chromogranin (n=15). One case of AFH and 1 case of PPMS showed focally strong coexpression of synaptophysin and ALK. AFH and PPMS show considerable clinicopathologic overlap. When supportive, the immunohistochemical findings described may aid in diagnosis before molecular confirmation. PPMS and AFH may be morphologic variants of the same clinicopathologic entity, which can show more immunophenotypic variability than previously reported.