Smoking-Related Interstitial Lung Disease: Historical Perspective and Advances in the Twenty-first Century.

In the twenty- first century, there is widespread agreement that in addition to lung cancer, emphysema, and chronic bronchitis, cigarette smoking causes accumulation of pigmented macrophages, interstitial fibrosis, and Langerhans cell proliferation in various permutations. These histologic changes remain subclinical in some patients and produce clinical manifestations and imaging abnormalities in others. Debate surrounds terminology of these lesions, which are often grouped together under the umbrella of "smoking-related interstitial lung disease." This review summarizes modern concepts in our understanding of these abnormalities and explains how the recognition of smoking-related interstitial fibrosis has advanced the field.

Assessment of Pathology Domain-Specific Knowledge of ChatGPT and Comparison to Human Performance.

CONTEXT.­: Artificial intelligence algorithms hold the potential to fundamentally change many aspects of society. Application of these tools, including the publicly available ChatGPT, has demonstrated impressive domain-specific knowledge in many areas, including medicine. OBJECTIVES.­: To understand the level of pathology domain-specific knowledge for ChatGPT using different underlying large language models, GPT-3.5 and the updated GPT-4. DESIGN.­: An international group of pathologists (n = 15) was recruited to generate pathology-specific questions at a similar level to those that could be seen on licensing (board) examinations. The questions (n = 15) were answered by GPT-3.5, GPT-4, and a staff pathologist that recently passed their Canadian pathology licensing exams. Participants were instructed to score answers on a 5-point scale and to predict which answer was written by ChatGPT. RESULTS.­: GPT-3.5 performed at a similar level to the staff pathologist, while GPT-4 outperformed both. The overall score for both GPT-3.5 and GPT-4 was within the range of meeting expectations for a trainee writing licensing examinations. In all but one question, the reviewers were able to correctly identify the answers generated by GPT-3.5. CONCLUSIONS.­: By demonstrating the ability of ChatGPT to answer pathology-specific questions at a level similar to (GPT-3.5) or exceeding (GPT-4) a trained pathologist, this study highlights the potential of large language models to be transformative in this space. In the future, more advanced iterations of these algorithms with increased domain-specific knowledge may have the potential to assist pathologists and enhance pathology resident training.

Differential diagnosis of IgG4-positive plasma cells in the lung.

The recognition of immunoglobulin G4-related disease (IgG4-RD) as an entity in the pancreaticobiliary tract was followed by a slew of papers describing inflammation and fibrosis containing IgG4-positive plasma cells in a variety of sites including the respiratory tract, leading to the hypothesis that these abnormalities were attributable to IgG4-RD. Predictably, pathologists began to see requests from clinicians to perform IgG4 immunohistochemistry in lung biopsies "to rule out IgG4-RD". Several years later, the notion that IgG4-RD would prove to be the underlying cause of a wide array of fibroinflammatory lesions in the lung has not panned out as promised. To the contrary, it has become clear that IgG4-positive plasma cells are not specific for IgG4-RD, and that large numbers of IgG4-positive plasma cells can be encountered in other well-defined entities, including inflammatory myofibroblastic tumor and nodular lymphoid hyperplasia, as well as in lymphoplasmacytic infiltrates in other entities, including connective tissue disease and idiopathic forms of interstitial lung disease. It has also become clear that raised serum IgG4 levels can occur in settings other than IgG4-RD. These observations suggest that true IgG4-RD of the lung is far less common than previously surmised. Pathologists must familiarize themselves with mimics of IgG4-RD in the lung and exercise caution before attributing lymphoplasmacytic infiltrates in the lung to IgG4-RD.

Preoperative predictors of spread through air spaces in lung cancer.

OBJECTIVE: Spread through air spaces (STAS) is a new histologic feature of invasion of non-small cell lung cancer that lacks sensitivity and specificity on frozen sections and is associated with higher recurrence and worse survival with sublobar resections. Our objective is to identify preoperative characteristics that are predictive of STAS to guide operative decisions. METHODS: From January 2018 through December 2021, 439 cT1-3N0 M0 patients with non-small cell lung cancer and a median age of 68 years, 255 (58%) women, who underwent primary surgery at our institution were included. Patients who received neoadjuvant therapy and whose STAS status was not documented were excluded. Age, sex, smoking status, tumor size, ground-glass opacities, maximum standardized uptake values, and molecular markers on preoperative biopsy were evaluated as preoperative markers. Comparisons between groups were conducted using standardized mean differences and random forest classification was used for prediction modeling. RESULTS: Of the 439 patients, 177 had at least 1 STAS-positive tumor, and 262 had no STAS-positive tumors. Overall, 179 STAS tumors and 293 non-STAS tumors were evaluated. Younger age (50 years or younger), solid tumor, size ≥2 cm, and maximum standardized uptake value ≥2.5 were independently predictive of STAS with prediction probabilities of 50%, 40%, 38%, and 40%, respectively. STAS tumors were more likely to harbor KRAS mutations and be PD-L1 negative. CONCLUSIONS: Young age (50 years or younger), larger (≥2 cm) solid tumors, high maximum standardized uptake values, and presence of KRAS mutation, are risk factors for STAS and can be considered for lobectomy. Smoking status and gender are still controversial risk factors for STAS.

Pericardial mesothelioma presenting as constrictive pericarditis.

A 46-year-old woman underwent pericardiocentesis and pericardial window for recurrent pericardial effusion. She presented 17 months later with signs and symptoms consistent with constrictive pericarditis. Cardiac magnetic resonance imaging revealed an infiltrative mass surrounding the pericardium. A transcutaneous core needle biopsy of the pericardium confirmed the diagnosis of pericardial mesothelioma.

Airway Injury Caused by Aspiration of Iron Sulfate Pills: A Series of 11 Cases.

It is not widely recognized that iron (ferrous sulfate) pill aspiration causes airway damage. Clinical diagnosis is challenging because patients are often unaware that they have aspirated a pill. The literature on this entity consists mainly of case reports. The aim of this study is to describe the clinical and pathologic features of iron pill aspiration in a series of 11 patients. A retrospective review of our pathology archives was performed to identify cases of iron pill aspiration (2013-2023). All available histologic and cytologic material was rereviewed. Clinical information was collected from the electronic medical record, and imaging studies were rereviewed. Eighteen endobronchial biopsies were identified from 11 patients (7 women and 4 men; mean age, 70 years; range, 44-82 years). Eight patients had corresponding cytology (20 specimens). Medication history was available in 9 of 11 patients, all of whom were taking iron sulfate pills. Two patients reported possible aspiration episodes; 4 had risk factors for aspiration. The diagnosis of iron pill aspiration was suspected prior to biopsy in only 1 case. Histologically, iron pill particles were yellow, golden brown, or gray, were elongated and crystal or fiber like, and stained strongly with an iron stain. Common histologic findings included mucosal ulceration, acute and/or chronic inflammation, fibrosis, and squamous metaplasia. Iron pill particles were also identified in 11 cytology specimens from 6 patients. On Papanicolaou staining, iron pill particles were yellow to golden, fiber like, refractile, and crystalline. Reactive epithelial cells, squamous metaplasia, and acute inflammation were common. The combination of iron pill intake and discolored mucosa on bronchoscopy is a potential clue to the diagnosis of iron pill aspiration. Pathologists should familiarize themselves with the appearance of iron pill particles in endobronchial biopsies and cytology specimens from the respiratory tract as this diagnosis is seldom suspected on clinical grounds, and most patients lack a history of aspiration.

Smoking-Related Interstitial Fibrosis (SRIF) in Patients Presenting With Diffuse Parenchymal Lung Disease.

OBJECTIVES: To describe the clinical, radiologic, and pathologic findings in cases where smoking-related interstitial fibrosis (SRIF) was diagnosed in surgical lung biopsy specimens from patients with clinical and imaging features of diffuse parenchymal lung disease (DPLD). METHODS: Cases were included in this study if patients had clinical and imaging evidence of DPLD and surgical lung biopsy specimens revealed SRIF. A dedicated multidisciplinary conference was held to correlate clinical, radiologic, and pathologic findings. RESULTS: Six cases met inclusion criteria; all six (five women/one man, aged 42-57 years, mean age 47 years) were either current smokers (five of six) or ex-smokers (one of six) and were evaluated for respiratory symptoms and abnormal pulmonary function tests, most commonly reduced forced vital capacity (n = 3) and diffusing capacity for carbon monoxide (n = 6). The most common imaging abnormalities were bilateral ground-glass opacities, which correlated with histopathologic SRIF. Follow-up of up to 10 years showed stable or improved clinical symptoms, pulmonary function tests, and radiologic findings with smoking cessation (three patients) or a decrease in smoking (three patients). No specific treatments were given, and those treated with empiric corticosteroid tapers did not show discernible responses. CONCLUSIONS: SRIF can present as clinically meaningful diffuse parenchymal lung disease in relatively young heavy smokers, characterized by bilateral ground-glass opacities and a stable clinical course.

Oil Red O Staining of Pulmonary Macrophages in Bronchoalveolar Lavage Specimens Is Not Specific for Vaping-Associated Lung Injury.

OBJECTIVES: Oil Red O (ORO) positivity in bronchoalveolar lavage (BAL) fluid macrophages in the setting of e-cigarette, or vaping, product use-associated acute lung injury (EVALI) has been frequently requested by clinicians based on rare reports and subsequent US Centers for Disease Control and Prevention guidelines. The aim of this study was to determine the specificity of ORO staining in BAL specimens with disease states other than EVALI. METHODS: Consecutive BAL specimens (October-December 2019) were stained with ORO. The lipid-laden macrophage index (LLMI) was calculated for each case. RESULTS: We studied BAL samples from 50 patients. Indications for BAL were surveillance bronchoscopy for lung transplantation (27/50), suspected infection (12/50), sarcoidosis/suspected sarcoidosis (3/50), nodules or ground-glass opacities (3/50), hemoptysis (2/50), asthma or eosinophilic pneumonia (2/50), and idiopathic pulmonary fibrosis (1/50). ORO staining was seen in BAL fluid macrophages in 45 of 50 cases (focal in 18, moderate in 23, diffuse in 4); LLMI ranged from 0 to 218. Using a threshold of LLMI of 85 or higher as positive, ORO was positive in 7 of 50 (14%) cases (range, 85-218). CONCLUSIONS: ORO staining in BAL fluid macrophages is not specific for EVALI. Even when an LLMI of 85 or higher is used as a threshold for positivity, ORO positivity occurs in a significant subset of non-vaping-related cases.

Targeting Doublecortin-Like Kinase 1 (DCLK1)-Regulated SARS-CoV-2 Pathogenesis in COVID-19.

Host factors play critical roles in SARS-CoV-2 infection-associated pathology and the severity of COVID-19. In this study, we systematically analyzed the roles of SARS-CoV-2-induced host factors, doublecortin-like kinase 1 (DCLK1), and S100A9 in viral pathogenesis. In autopsied subjects with COVID-19 and pre-existing chronic liver disease, we observed high levels of DCLK1 and S100A9 expression and immunosuppressive (DCLK1+S100A9+CD206+) M2-like macrophages and N2-like neutrophils in lungs and livers. DCLK1 and S100A9 expression were rarely observed in normal controls, COVID-19-negative subjects with chronic lung disease, or COVID-19 subjects without chronic liver disease. In hospitalized patients with COVID-19, we detected 2 to 3-fold increased levels of circulating DCLK1+S100A9+ mononuclear cells that correlated with disease severity. We validated the SARS-CoV-2-dependent generation of these double-positive immune cells in coculture. SARS-CoV-2-induced DCLK1 expression correlated with the activation of ß-catenin, a known regulator of the DCLK1 promoter. Gain and loss of function studies showed that DCLK1 kinase amplified live virus production and promoted cytokine, chemokine, and growth factor secretion by peripheral blood mononuclear cells. Inhibition of DCLK1 kinase blocked pro-inflammatory caspase-1/interleukin-1ß signaling in infected cells. Treatment of SARS-CoV-2-infected cells with inhibitors of DCLK1 kinase and S100A9 normalized cytokine/chemokine profiles and attenuated DCLK1 expression and ß-catenin activation. In conclusion, we report previously unidentified roles of DCLK1 in augmenting SARS-CoV-2 viremia, inflammatory cytokine expression, and dysregulation of immune cells involved in innate immunity. DCLK1 could be a potential therapeutic target for COVID-19, especially in patients with underlying comorbid diseases associated with DCLK1 expression. IMPORTANCE High mortality in COVID-19 is associated with underlying comorbidities such as chronic liver diseases. Successful treatment of severe/critical COVID-19 remains challenging. Herein, we report a targetable host factor, DCLK1, that amplifies SARS-CoV-2 production, cytokine secretion, and inflammatory pathways via activation of ß-catenin(p65)/DCLK1/S100A9/NF-κB signaling. Furthermore, we observed in the lung, liver, and blood an increased prevalence of immune cells coexpressing DCLK1 and S100A9, a myeloid-derived proinflammatory protein. These cells were associated with increased disease severity in COVID-19 patients. Finally, we used a novel small-molecule inhibitor of DCLK1 kinase (DCLK1-IN-1) and S100A9 inhibitor (tasquinimod) to decrease virus production in vitro and normalize hyperinflammatory responses known to contribute to disease severity in COVID-19.

SARS-CoV-2 infection produces chronic pulmonary epithelial and immune cell dysfunction with fibrosis in mice.

A subset of individuals who recover from coronavirus disease 2019 (COVID-19) develop post-acute sequelae of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (PASC), but the mechanistic basis of PASC-associated lung abnormalities suffers from a lack of longitudinal tissue samples. The mouse-adapted SARS-CoV-2 strain MA10 produces an acute respiratory distress syndrome in mice similar to humans. To investigate PASC pathogenesis, studies of MA10-infected mice were extended from acute to clinical recovery phases. At 15 to 120 days after virus clearance, pulmonary histologic findings included subpleural lesions composed of collagen, proliferative fibroblasts, and chronic inflammation, including tertiary lymphoid structures. Longitudinal spatial transcriptional profiling identified global reparative and fibrotic pathways dysregulated in diseased regions, similar to human COVID-19. Populations of alveolar intermediate cells, coupled with focal up-regulation of profibrotic markers, were identified in persistently diseased regions. Early intervention with antiviral EIDD-2801 reduced chronic disease, and early antifibrotic agent (nintedanib) intervention modified early disease severity. This murine model provides opportunities to identify pathways associated with persistent SARS-CoV-2 pulmonary disease and test countermeasures to ameliorate PASC.

Recurrence of primary disease following lung transplantation.

Lung transplant has become definitive treatment for patients with several end-stage lung diseases. Since the first attempted lung transplantation in 1963, survival has significantly improved due to advancement in immunosuppression, organ procurement, ex vivo lung perfusion, surgical techniques, prevention of chronic lung allograft dysfunction and bridging to transplant using extracorporeal membrane oxygenation. Despite a steady increase in number of lung transplantations each year, there is still a huge gap between demand and supply of organs available, and work continues to select recipients with potential for best outcomes. According to review of the literature, there are some rare primary diseases that may recur following transplantation. As the number of lung transplants increase, we continue to identify disease processes at highest risk for recurrence, thus shaping our future approaches. While the aim of lung transplantation is improving survival and quality of life, choosing the best recipients is crucial due to a shortage of donated organs. Here we discuss the common disease processes that recur and highlight its impact on overall outcome following lung transplantation.

Prospective cohort of cryobiopsy in interstitial lung diseases: a single center experience.

RATIONALE: Transbronchial cryobiopsy has been increasingly used to diagnose interstitial lung diseases. However, there is uncertainty regarding its accuracy and risks, mainly due to a paucity of prospective or randomized trials comparing cryobiopsy to surgical biopsy. OBJECTIVES: To evaluate the diagnostic yield and complications of cryobiopsy in patients selected by multidisciplinary discussion. METHODS: This was a prospective cohort from 2017 to 2019. We included consecutive patients with suspected interstitial lung diseases being considered for lung biopsy presented at our multidisciplinary meeting. MEASUREMENTS AND MAIN RESULTS: Of 112 patients, we recommended no biopsy in 31, transbronchial forceps biopsy in 16, cryobiopsy in 54 and surgical biopsy in 11. By the end of the study, 34 patients had had cryobiopsy and 24 patients, surgical biopsy. Overall pathologic and multidisciplinary diagnostic yield of cryobiopsy was 47.1% and 61.8%, respectively. The yield increased over time for both pathologic (year 1: 28.6%, year 2: 54.5%, year 3: 66.7%, p = 0.161) and multidisciplinary (year 1: 50%, year 2: 63.6%, year 3: 77.8%, p = 0.412) diagnosis. Overall rate of grade 4 bleeding after cryobiopsy was 11.8%. Cryobiopsy required less chest tube placement (11.8% vs 100%, p < 0.001) and less hospitalizations compared to surgical biopsy (26.5% vs 95.7%, p < 0.001), but hospitalized patients had a longer median hospital stay (2 days vs 1 day, p = 0.004). CONCLUSIONS: Diagnostic yield of cryobiopsy increased over time but the overall grade 4 bleeding rate was 11.8%.

The state of the art for artificial intelligence in lung digital pathology.

Lung diseases carry a significant burden of morbidity and mortality worldwide. The advent of digital pathology (DP) and an increase in computational power have led to the development of artificial intelligence (AI)-based tools that can assist pathologists and pulmonologists in improving clinical workflow and patient management. While previous works have explored the advances in computational approaches for breast, prostate, and head and neck cancers, there has been a growing interest in applying these technologies to lung diseases as well. The application of AI tools on radiology images for better characterization of indeterminate lung nodules, fibrotic lung disease, and lung cancer risk stratification has been well documented. In this article, we discuss methodologies used to build AI tools in lung DP, describing the various hand-crafted and deep learning-based unsupervised feature approaches. Next, we review AI tools across a wide spectrum of lung diseases including cancer, tuberculosis, idiopathic pulmonary fibrosis, and COVID-19. We discuss the utility of novel imaging biomarkers for different types of clinical problems including quantification of biomarkers like PD-L1, lung disease diagnosis, risk stratification, and prediction of response to treatments such as immune checkpoint inhibitors. We also look briefly at some emerging applications of AI tools in lung DP such as multimodal data analysis, 3D pathology, and transplant rejection. Lastly, we discuss the future of DP-based AI tools, describing the challenges with regulatory approval, developing reimbursement models, planning clinical deployment, and addressing AI biases. © 2022 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Giant Cell Interstitial Pneumonia In Native, Transplanted And Re-Transplanted Lungs 8 Years Apart Without Known Hard Metal Exposure.

Pneumoconioses are a group of non-neoplastic pulmonary disorders caused by inhaled inorganic particles. Well-described pneumoconioses include asbestosis, silicosis, coal worker's pneumoconiosis, chronic beryllium disease, and hard metal lung disease. Giant cell interstitial pneumonia (GIP) is a distinctive and rare pneumoconiosis most frequently found in workers exposed to hard metals, primarily cobalt and tungsten carbide. The pathologic picture is considered virtually pathognomonic for hard metal lung disease, although this dogma has been questioned by a few reports of giant cell interstitial pneumonia in patients without apparent hard metal exposure. Giant cell interstitial pneumonia is even rarer in lung transplant recipients. Here, we present a patient without known hard metal exposure who was found to have persistent giant cell interstitial pneumonia in native, transplanted and re-transplanted lungs 8 years apart.

COVID-19-Associated cardiac pathology at the postmortem evaluation: a collaborative systematic review.

BACKGROUND: Many postmortem studies address the cardiovascular effects of COVID-19 and provide valuable information, but are limited by their small sample size. OBJECTIVES: The aim of this systematic review is to better understand the various aspects of the cardiovascular complications of COVID-19 by pooling data from a large number of autopsy studies. DATA SOURCES: We searched the online databases Ovid EBM Reviews, Ovid Embase, Ovid Medline, Scopus, and Web of Science for concepts of autopsy or histopathology combined with COVID-19, published between database inception and February 2021. We also searched for unpublished manuscripts using the medRxiv services operated by Cold Spring Harbor Laboratory. STUDY ELIGIBILITY CRITERIA: Articles were considered eligible for inclusion if they reported human postmortem cardiovascular findings among individuals with a confirmed SARS coronavirus type 2 (CoV-2) infection. PARTICIPANTS: Confirmed COVID-19 patients with post-mortem cardiovascular findings. INTERVENTIONS: None. METHODS: Studies were individually assessed for risk of selection, detection, and reporting biases. The median prevalence of different autopsy findings with associated interquartile ranges (IQRs). RESULTS: This review cohort contained 50 studies including 548 hearts. The median age of the deceased was 69 years. The most prevalent acute cardiovascular findings were myocardial necrosis (median: 100.0%; IQR, 20%-100%; number of studies = 9; number of patients = 64) and myocardial oedema (median: 55.5%; IQR, 19.5%-92.5%; number of studies = 4; number of patients = 46). The median reported prevalence of extensive, focal active, and multifocal myocarditis were all 0.0%. The most prevalent chronic changes were myocyte hypertrophy (median: 69.0%; IQR, 46.8%-92.1%) and fibrosis (median: 35.0%; IQR, 35.0%-90.5%). SARS-CoV-2 was detected in the myocardium with median prevalence of 60.8% (IQR 40.4-95.6%). CONCLUSIONS: Our systematic review confirmed the high prevalence of acute and chronic cardiac pathologies in COVID-19 and SARS-CoV-2 cardiac tropism, as well as the low prevalence of myocarditis in COVID-19.

Usual interstitial pneumonia (UIP): a clinically significant pathologic diagnosis.

This editorial focuses on common issues that surround the diagnosis of usual interstitial pneumonia (UIP), a clinically significant pathologic diagnosis. Most of these issues stem from conflation of the pathologically defined entity UIP with the clinically defined entity IPF. A pathologic or radiologic diagnosis of UIP is required for the clinical/multidisciplinary diagnosis of idiopathic pulmonary fibrosis (IPF) but it has also been described in several other clinical settings. I offer my viewpoint on 5 important questions. 1. Is UIP a diagnosis or a "pattern"? ANSWER: UIP is a pathologic diagnosis and is better conceptualized as a "pattern" than as a specific clinical entity. Since all cases of UIP require pattern recognition, adding the word "pattern" to UIP is redundant. 2. Is pathology the gold standard for UIP? ANSWER: Yes. 3. How do you "prove" etiology of a given case of UIP? ANSWER: "Soft" histologic features can raise the possibility of certain etiologies but the final determination of etiology comes from the multidisciplinary team. With few exceptions, there are no findings pathognomonic for any etiology in UIP. 4. Does UIP imply IPF? ANSWER: No. 5. What should we do when pathology and HRCT are discordant? ANSWER: This depends on the specifics of the discrepancy. When HRCT suggests a non-UIP diagnosis such as NSIP and histology shows UIP, histology has been shown to predict prognosis in multiple studies. In other settings, the radiologic impression based on HRCT is often proven to be incorrect by the histologic findings.

A model of persistent post SARS-CoV-2 induced lung disease for target identification and testing of therapeutic strategies.

COVID-19 survivors develop post-acute sequelae of SARS-CoV-2 (PASC), but the mechanistic basis of PASC-associated lung abnormalities suffers from a lack of longitudinal samples. Mouse-adapted SARS-CoV-2 MA10 produces an acute respiratory distress syndrome (ARDS) in mice similar to humans. To investigate PASC pathogenesis, studies of MA10-infected mice were extended from acute disease through clinical recovery. At 15-120 days post-virus clearance, histologic evaluation identified subpleural lesions containing collagen, proliferative fibroblasts, and chronic inflammation with tertiary lymphoid structures. Longitudinal spatial transcriptional profiling identified global reparative and fibrotic pathways dysregulated in diseased regions, similar to human COVID-19. Populations of alveolar intermediate cells, coupled with focal upregulation of pro-fibrotic markers, were identified in persistently diseased regions. Early intervention with antiviral EIDD-2801 reduced chronic disease, and early anti-fibrotic agent (nintedanib) intervention modified early disease severity. This murine model provides opportunities to identify pathways associated with persistent SARS-CoV-2 pulmonary disease and test countermeasures to ameliorate PASC.

Does histological assessment accurately distinguish separate primary lung adenocarcinomas from intrapulmonary metastases? A study of paired resected lung nodules in 32 patients using a routine next-generation sequencing panel for driver mutations.

AIM: Various approaches have been reported for distinguishing separate primary lung adenocarcinomas from intrapulmonary metastases in patients with two lung nodules. The aim of this study was to determine whether histological assessment is reliable and accurate in distinguishing separate primary lung adenocarcinomas from intrapulmonary metastases using routine molecular findings as an adjunct. METHODS: We studied resected tumour pairs from 32 patients with lung adenocarcinomas in different lobes. In 15 of 32 tumour pairs, next-generation sequencing (NGS) for common driver mutations was performed on both nodules. The remainder of tumour pairs underwent limited NGS, or EGFR genotyping. Tumour pairs with different drivers (or one driver/one wild-type) were classified as molecularly unrelated, while those with identical low-frequency drivers were classified as related. Three pathologists independently and blinded to the molecular results categorised tumour pairs as related or unrelated based on histological assessment. RESULTS: Of 32 pairs, 15 were classified as related by histological assessment, and 17 as unrelated. Of 15 classified as related by histology, 6 were classified as related by molecular analysis, 4 were unrelated and 5 were indeterminate. Of 17 classified as unrelated by histology, 14 were classified as unrelated by molecular analysis, none was related and 3 were indeterminate. Histological assessment of relatedness was inaccurate in 4/32 (12.5%) tumour pairs. CONCLUSIONS: A small but significant subset of two-nodule adenocarcinoma pairs is inaccurately judged as related by histological assessment, and can be proven to be unrelated by molecular analysis (driver gene mutations), leading to significant downstaging.

SMARCA4-Deficient Undifferentiated Tumor Diagnosed on Adrenal Sampling.

OBJECTIVES: SMARCA4-deficient undifferentiated tumor has distinct clinicopathologic features. We describe our experience with primary diagnosis on adrenal sampling. METHODS: We collected six SMARCA4-deficient undifferentiated tumors diagnosed on adrenal sampling. Immunostains for SMARCA4, SF-1, inhibin, calretinin, S-100 protein, EMA, and TTF-1 were performed. A control group of 63 primary adrenocortical tumors was also immunostained. RESULTS: Patients included four men and two women (aged 52-77 years). Five had unilateral adrenal masses and one bilateral (range, 2.4-9.6 cm). Five had pulmonary masses, and one had a midline mediastinal mass. All cases had a monotonous epithelioid appearance and variable rhabdoid morphology. Immunophenotypically, all six cases had loss of nuclear SMARCA4 expression and no staining for SF-1, inhibin, calretinin, or S-100 protein. Variable EMA immunoreactivity was present in four of six cases and focal nuclear TTF-1 expression in one of six. All 63 adrenocortical neoplasms had retained nuclear SMARCA4 expression. CONCLUSIONS: SMARCA4-deficient undifferentiated tumor may present in the adrenal gland, and this series likely represents metastases from thoracic primaries. Because of the frequent absence of lineage marker expression, knowledge of the characteristic clinical presentation, the rhabdoid morphology, and the typical immunophenotype (loss of SMARCA4/BRG1) allow for appropriate distinction from adrenocortical carcinoma.