Review of the Pathologic Characteristics in Myhre Syndrome: Gain-of-Function Pathogenic Variants in SMAD4 cause a Multisystem Fibroproliferative Response.

Background: Myhre syndrome, caused by pathogenic variants in SMAD4, is characterized by compact body habitus with short stature, distinctive craniofacial appearance, stiff skin, cardiovascular abnormalities (valve stenosis, coarctation, hypoplasia, or stenosis of aorta), effusions of potential spaces (pericardium, pleura, peritoneum), restricted movement of the joints (including thorax), and hearing loss. Lung and airway disease has been reported, but not always well-defined, to include interstitial lung disease, large airway obstruction, and pulmonary arterial hypertension. Excessive fibroproliferation of tissues especially following trauma or surgical instrumentation has been recognized, although these may also present spontaneously. Method: We report the pathologic features of 1 new patient with progressive choanal stenosis, and 22 literature cases, including the expanded history of 5 patients (3 who died). Results: Examination of patient tissues documents cellular fibroproliferation and deposition of excessive extracellular matrix explaining some of the observed clinical features of Myhre syndrome. Conclusion: Excessive fibrosis is noted in multiple tissues, especially heart, lung, and upper and lower airways. Our research provides the first systematic review to provide a knowledge base of gross and pathologic findings in Myhre syndrome.

Diagnostic Accuracy of Endobronchial Optical Coherence Tomography for the Microscopic Diagnosis of Usual Interstitial Pneumonia.

Rationale: Early, accurate diagnosis of interstitial lung disease (ILD) informs prognosis and therapy, especially in idiopathic pulmonary fibrosis (IPF). Current diagnostic methods are imperfect. High-resolution computed tomography has limited resolution, and surgical lung biopsy (SLB) carries risks of morbidity and mortality. Endobronchial optical coherence tomography (EB-OCT) is a low-risk, bronchoscope-compatible modality that images large lung volumes in vivo with microscopic resolution, including subpleural lung, and has the potential to improve the diagnostic accuracy of bronchoscopy for ILD diagnosis. Objectives: We performed a prospective diagnostic accuracy study of EB-OCT in patients with ILD with a low-confidence diagnosis undergoing SLB. The primary endpoints were EB-OCT sensitivity/specificity for diagnosis of the histopathologic pattern of usual interstitial pneumonia (UIP) and clinical IPF. The secondary endpoint was agreement between EB-OCT and SLB for diagnosis of the ILD fibrosis pattern. Methods: EB-OCT was performed immediately before SLB. The resulting EB-OCT images and histopathology were interpreted by blinded, independent pathologists. Clinical diagnosis was obtained from the treating pulmonologists after SLB, blinded to EB-OCT. Measurements and Main Results: We enrolled 31 patients, and 4 were excluded because of inconclusive histopathology or lack of EB-OCT data. Twenty-seven patients were included in the analysis (16 men, average age: 65.0 yr): 12 were diagnosed with UIP and 15 with non-UIP ILD. Average FVC and DlCO were 75.3% (SD, 18.5) and 53.5% (SD, 16.4), respectively. Sensitivity and specificity of EB-OCT was 100% (95% confidence interval, 75.8-100.0%) and 100% (79.6-100%), respectively, for both histopathologic UIP and clinical diagnosis of IPF. There was high agreement between EB-OCT and histopathology for diagnosis of ILD fibrosis pattern (weighted κ: 0.87 [0.72-1.0]). Conclusions: EB-OCT is a safe, accurate method for microscopic ILD diagnosis, as a complement to high-resolution computed tomography and an alternative to SLB.

Clinical Benefit of Tyrosine Kinase Inhibitors in Advanced Lung Cancer with EGFR-G719A and Other Uncommon EGFR Mutations.

The optimal management of advanced non-small cell lung cancer (NSCLC) with noncanonical epidermal growth factor receptor (EGFR) mutations (i.e., exon 19 deletion and exon 21 L858R) is constrained by the heterogeneous behavior of individual uncommon mutations and limited prospective clinical data in this setting. Despite encouraging results with osimertinib from a recently published phase II trial from South Korea, afatinib remains the only currently approved drug for patients with tumors harboring uncommon EGFR mutations (i.e., S768I, L861Q, and/or G719X). When used at the standard dose of 40 mg daily, afatinib is associated with significant rates of treatment-related adverse events, leading to frequent dose reductions and treatment discontinuations. We report a case of a woman with advanced NSCLC harboring EGFR-G719A mutation treated with afatinib (at an off-label pulse dose strategy that merits further evaluation in prospective studies) with sustained partial response for 20 months with manageable expected toxicities. Subsequent disease progression was mediated by off-target pan-EGFR inhibitor (including osimertinib)-resistant KRAS mutation and not by acquisition of EGFR-T790M. We further present the current state of evidence in the literature behind use of first-, second-, and third-generation tyrosine kinase inhibitors and summarize the evolving spectrum of activity ascribed to osimertinib (and newer EGFR inhibitors with a more favorable therapeutic window and intracranial penetration) in this population of patients with advanced NSCLC and uncommon EGFR mutations. KEY POINTS: Uncommon EGFR mutations characterize a heterogeneous group of patients with advanced non-small cell lung cancer (NSCLC). Afatinib is the only currently U.S. Food and Drug Administration-approved drug for management of advanced NSCLC with uncommon EGFR mutations (S768I, L861Q, and/or G719X). Afatinib treatment at 40 mg daily is associated with high rates of adverse events and dose reductions; alternative strategies including pulse intermittent dosing should be evaluated prospectively. Osimertinib (with favorable safety profile and intracranial penetration) has shown promising results in this population in a phase II trial from South Korea; additional trials are ongoing.

The Growth Rate of Subsolid Lung Adenocarcinoma Nodules at Chest CT.

Background Confirming that subsolid adenocarcinomas show exponential growth is important because it would justify using volume doubling time to assess their growth. Purpose To test whether the growth of lung adenocarcinomas manifesting as subsolid nodules at chest CT is accurately represented by an exponential model. Materials and Methods Patients with lung adenocarcinomas manifesting as subsolid nodules surgically resected between January 2005 and May 2018, with three or more longitudinal CT examinations before resection, were retrospectively included. Overall volume (for all nodules) and solid component volume (for part-solid nodules) were measured over time. A linear mixed-effects model was used to identify the growth pattern (linear, exponential, quadratic, or power law) that best represented growth. The interactions between nodule growth and clinical, CT morphologic, and pathologic parameters were studied. Results Sixty-nine patients (mean age, 70 years ± 9 [standard deviation]; 48 women) with 74 lung adenocarcinomas were evaluated. Overall growth and solid component growth were better represented by an exponential model (adjusted R2 = 0.89 and 0.95, respectively) than by a quadratic model (r2 = 0.88 and 0.93, respectively), a linear model (r2 = 0.87 and 0.92, respectively), or a power law model (r2 = 0.82 and 0.93, respectively). Faster overall volume growth was associated with a history of lung cancer (P < .001), a baseline nodule volume less than 500 mm3 (P = .03), and histologic findings of invasive adenocarcinoma (P < .001). The median volume doubling time of noninvasive adenocarcinoma was significantly longer than that of invasive adenocarcinoma (939 days [interquartile range, 588-1563 days] vs 678 days [interquartile range, 392-916 days], respectively; P = .01). Conclusion The overall volume growth of adenocarcinomas manifesting as subsolid nodules at chest CT was best represented by an exponential model compared with the other tested models. This justifies the use of volume doubling time for the growth assessment of these nodules. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Kuriyama and Yanagawa in this issue.

Diagnostic value of biopsy sampling in predicting histology in patients with diffuse malignant pleural mesothelioma.

BACKGROUND: The classification of diffuse malignant mesothelioma into epithelioid, biphasic, and sarcomatoid types is based on histologic patterns. The diagnosis is made on biopsies, and because of intratumoral heterogeneity, they may not be representative of the entire tumor. The number and volume of biopsies needed to reach diagnostic accuracy in diffuse malignant mesothelioma and their prognostic value remain unclear. METHODS: This study examined 759 consecutive patients with pleural diffuse malignant mesothelioma treated by pleurectomy/decortication or extrapleural pneumonectomy for the presence of epithelioid and/or sarcomatoid histology and classified both the presurgery biopsies (core-needle or thoracoscopic) and surgical resection specimens. The number and volume of biopsies were correlated with pre- and postsurgery histologies and overall survival. RESULTS: Diffuse malignant mesothelioma was classified as epithelioid (76%), biphasic (18%), sarcomatoid (5%), or indeterminate (1%) in biopsies and as epithelioid (64%), biphasic (32%), and sarcomatoid (4%) in surgical resection specimens (overall concordance, 80.6%). The positive likelihood ratios were 2.4, 13.6, and 90.1 for biopsies with epithelioid, biphasic, and sarcomatoid histologies, respectively. Concordant histologies between biopsies and resections were associated with a higher number of biopsies (median tissue blocks for concordant histologies vs discordant histologies, 3 vs 2; P < .002) but were less associated with a higher volume (median, 1.2 vs 1.1 cm3 ; P = .06). In a multivariate analysis, overall survival was independently predicted by histology in the resection specimen (P < .0001) but not in the biopsy (P = .09). CONCLUSIONS: In contrast to epithelioid histology, sarcomatoid histology in biopsies is highly accurate. Despite intratumoral heterogeneity, the accuracy of histologic classification increases with the number of tissue blocks examined, emphasizing the diagnostic value of extensive sampling by presurgery biopsies.

Invariant Natural Killer T-Cells and Total CD1d Restricted Cells Differentially Influence Lipid Metabolism and Atherosclerosis in Low Density Receptor Deficient Mice.

Natural killer T (NKT) cells are a distinct subset of lymphocytes that bridge the innate and adaptive immune response and can be divided into type I invariant NKT cells (iNKT) and type II NKT cells. The objective of this study is to examine the effects of NKT cell on lipid metabolism and the initiation and progression of atherosclerosis in LDL receptor deficient (LDLR-/-) mice. Mice were fed an atherogenic diet for 4 or 8 weeks and plasma lipids, lipoproteins, and atherosclerosis were measured. The selective absence of iNKT cells in Jα18-/-LDLR-/- mice led to an increase in plasma cholesterol levels in female mice. Transgenic Vα14tg/LDLR-/- mice with elevated numbers of iNKT cells had increased late atherosclerosis of the innominate artery, though absence of either iNKT cells or all NKT cells and other CD1d expressing cells had varying effects on atherosclerotic lesion burden in the ascending aortic arch and aortic root. These studies not only highlight the potential modulatory role played by NKT cells in atherosclerosis and lipid metabolism, but also raise the possibility that divergent roles may be played by iNKT and CD1d restricted cells such as type II NKT cells or other CD1d expressing cells.

Software-based risk stratification of pulmonary adenocarcinomas manifesting as pure ground glass nodules on computed tomography.

OBJECTIVES: To assess the performance of the "Computer-Aided Nodule Assessment and Risk Yield" (CANARY) software in the differentiation and risk assessment of histological subtypes of lung adenocarcinomas manifesting as pure ground glass nodules on computed tomography (CT). METHODS: 64 surgically resected and histologically proven adenocarcinomas manifesting as pure ground-glass nodules on CT were assessed using CANARY software, which classifies voxel-densities into three risk components (low, intermediate, and high risk). Differences in risk components between histological adenocarcinoma subtypes were analysed. To determine the optimal threshold reflecting the presence of an invasive focus, sensitivity, specificity, negative predictive value, and positive predictive value were calculated. RESULTS: 28/64 (44%) were adenocarcinomas in situ (AIS); 26/64 (41%) were minimally invasive adenocarcinomas (MIA); and 10/64 (16%) were invasive ACs (IAC). The software showed significant differences in risk components between histological subtypes (P<0.001-0.003). A relative volume of 45% or less of low-risk components was associated with histological invasiveness (specificity 100%, positive predictive value 100%). CONCLUSIONS: CANARY-based risk assessment of ACs manifesting as pure ground glass nodules on CT allows the differentiation of their histological subtypes. A threshold of 45% of low-risk components reflects invasiveness in these groups. KEY POINTS: • CANARY-based risk assessment allows the differentiation of their histological subtypes. • 45% or less of low-risk component reflects histological invasiveness. • CANARY has potential role in suspected adenocarcinomas manifesting as pure ground-glass nodules.

Binary subclassification scheme (AUS-Nuclear versus AUS-Other) adequately risk-stratifies thyroid fine needle aspiration specimens classified as Atypia of Undetermined Significance.

INTRODUCTION: The Bethesda System for Reporting Thyroid Cytopathology previously described 4 subclasses of atypia within the Atypia of Undetermined Significance (AUS) category: nuclear (AUS-Nuc), architectural (AUS-A), oncocytic (AUS-Onc), and atypia not otherwise specified (AUS-NOS). Accumulating evidence supports a binary AUS subclassification scheme based primarily on the presence of nuclear atypia only. The purpose of this study is to compare the risk stratification of binary versus 4-tier AUS subclassification systems among AUS nodules with molecular and/or histologic follow-up. MATERIALS AND METHODS: Thyroid aspirates classified as AUS and tested using Afirma (Veracyte, Inc.) between 6/2013 and 7/2021 were included. For resected nodules, histological classification was considered as the final outcome. For unresected nodules, benign Afirma results were considered low-risk outcomes, similar to histologically benign nodules. Suspicious or nondiagnostic Afirma results were considered indeterminate outcomes. The prevalence of outcomes warranting surgery (noninvasive follicular thyroid neoplasm with papillary-like nuclear features [NIFTP] or cancer) was calculated for each AUS subclass. RESULTS: A total of 559 AUS nodules with Afirma testing were identified. Excluding nodules with indeterminate molecular outcomes, NIFTP/cancer prevalence for AUS-Nuc was 21% (57/266), which was higher than that for AUS-A (6%, 11/188), AUS-Onc (8%, 4/53), and AUS-NOS (0%, 0/9). A binary AUS subclassification scheme based on nuclear atypia showed a significant difference in NIFTP/cancer prevalence (21% versus 6%, P < 0.0001). CONCLUSIONS: Binary reporting of AUS subclasses based on nuclear atypia distinguishes cases with a higher risk of NIFTP/cancer. There is a low but non-negligible prevalence of NIFTP/cancer in cases without nuclear atypia.

Insulinoma-associated protein-1 (INSM-1) is a useful diagnostic marker for the evaluation of primary thymic neuroendocrine neoplasms: an immunohistochemical study of 27 cases.

Insulinoma-associated protein 1 (INSM1) immunohistochemistry has been established as a sensitive and reliable immunohistochemical marker for detecting neuroendocrine differentiation in tumors across various organ systems. However, this marker has not been adequately investigated in primary thymic neuroendocrine tumors. We have studied a series of 27 cases of primary neuroendocrine carcinomas of the thymus, including 3 typical carcinoids, 18 atypical carcinoids, 4 large cell neuroendocrine carcinomas, and 2 small cell carcinomas. Immunostaining on whole tissue sections for INSM-1 was evaluated. Results of immunostaining for chromogranin and synaptophysin were also evaluated. 26/27 tumors (96%) demonstrated nuclear positivity for INSM1. 18 tumors (67%) showed strong and diffuse nuclear staining (3 +), 3 tumors (11%) moderate (2 +) nuclear staining, and 5 tumors (19%) showed weak (1 +) nuclear staining. The average percentage of tumor cells positive for INSM1 was 76%. Only one tumor, a small cell carcinoma, was negative. All tumors were positive for synaptophysin, and 26/27 (96%) were positive for chromogranin A. This study confirms that INSM1 immunohistochemistry is a sensitive marker of neuroendocrine differentiation in primary thymic neuroendocrine neoplasms and demonstrates similar performance characteristics compared to other organ systems. The nuclear staining with this marker offers the advantage of eliminating some of the ambiguity in the interpretation sometimes encountered with other markers. An added advantage is the consistent staining across the entire spectrum of neuroendocrine tumors of this organ.

Gastrointestinal stromal tumors in fine-needle aspiration biopsies.

Gastrointestinal stromal tumors (GISTs), although rare, are the most common mesenchymal neoplasms of the gastrointestinal tract. Their potential for malignancy underscores the significance of identifying them through cytomorphologic findings and pertinent immunohistochemical markers. GISTs can emerge anywhere along the gastrointestinal tract with a predilection for the stomach. The clinical manifestations vary from nonspecific abdominal symptoms to incidental discovery during diagnostic interventions for unrelated signs and symptoms. Cytologically, GIST aspirates contain spindle or epithelioid cells with immunoreactivity for CD117/c-KIT, DOG-1, and CD34. Molecularly, KIT or PDGFRA mutations are prevalent, guiding targeted therapy with tyrosine kinase inhibitors. Distinct subtypes like succinate dehydrogenase-deficient GISTs pose challenges, often affecting younger individuals and displaying unique features. Histologically, GISTs are graded by mitotic rates, aiding prognostication. Distinguishing GISTs from similar entities is pivotal, necessitating attention to their immunostaining patterns for making an accurate diagnosis and molecular alterations for effectively planning treatment. Common differential diagnoses include leiomyoma, schwannoma, and solitary fibrous tumor. This article presents a classic GIST case and showcases relatively simple diagnostic clues for identifying similar lesions that may occur in diverse locations.

Imaging of Small Airways Disease.

Bronchiolitis refers to a small airways disease and may be classified by etiology and histologic features. In cellular bronchiolitis inflammatory cells involve the small airway wall and peribronchiolar alveoli and manifest on CT as centrilobular nodules of solid or ground glass attenuation. Constrictive bronchiolitis refers to luminal narrowing by concentric fibrosis. Direct CT signs of small airway disease include centrilobular nodules and branching tree-in-bud opacities. An indirect sign is mosaic attenuation that may be exaggerated on expiratory CT and represent air trapping. Imaging findings can be combined with clinical and pathologic data to facilitate a more accurate diagnosis.

Comparative genomic and immunopathologic analysis of lung adenocarcinomas with and without cytology-proven malignant pleural effusions.

BACKGROUND: Lung cancer complicated by malignant pleural effusions (MPEs) is associated with significantly increased morbidity and mortality, yet the mechanisms of MPE development remain poorly understood. This study sought to elucidate whether there were specific genomic alterations and/or immunologic biomarkers associated with the presence of MPEs. METHODS: Analysis of comprehensive genomic and immunologic profiling for 275 locally advanced (stage III) or advanced (stage IV) lung adenocarcinomas was subcategorized into cytology-confirmed MPE-positive (MPE+; n = 139 stage IV) and MPE-negative (MPE-; n = 30 stage III + n = 106 stage IV) groups. RESULTS: Smoking frequency (p = .0001) and tumor mutational burden (p < .001) were demonstrated to be lower in the MPE+ group compared to the MPE- group. Median overall survival in the MPE+ group was shorter than in the MPE- group across all data (2.0 vs. 5.5 years; p < .0001) and for smokers (1.2 vs. 6.4 years; p < .0001). There were a number of differences at the genomic level across all cases and when stratifying by smoking status, including a higher frequency of EGFR mutations and a lower frequency of STK11 mutations in the MPE+ cohort. Finally, investigation of the comutational profiles of tumors by MPE status revealed differences in TP53- and STK11-mutant tumors between the two groups. CONCLUSIONS: Overall, these findings imply that there are both clinical and genetic factors associated with advanced lung adenocarcinoma MPEs. Future studies of these alterations may prove important both for understanding the pathophysiology of MPE development in advanced cancer and for the earlier detection of at-risk patients.

Rapid examination of lung tissues by nonlinear microscopy.

OBJECTIVES: Traditional histopathology is a time-intensive and labor-intensive process involving tissue formalin fixation, paraffin embedding, and microtoming into thin sections for H&E staining. Frozen section analysis is a modality used during surgery to quickly evaluate tissue, but it has limitations, such as the size and number of the specimens that can be analyzed as well as difficulties with fatty and bony tissues. Our objective was to investigate the performance of nonlinear microscopy, a fluorescence microscopy technique, for the rapid examination of resected lung tumors. METHODS: In this proof-of-principle study, nonlinear microscopy imaging of resected lung tissue was performed on a total of 73 tissue specimens collected from 13 patients who underwent lobectomy, segmentectomy, or wedge resection for pulmonary nodules. RESULTS: Two pathologists reviewed the digital nonlinear microscopy images in comparison to the corresponding histopathologic H&E slides from a variety of pulmonary pathologies. CONCLUSIONS: This study demonstrated that nonlinear microscopy readily replicates traditional H&E staining for both lung tumors and nonneoplastic pulmonary structures. Nonlinear microscopy provides many advantages over frozen section analysis and is an optical imaging platform that has the potential to augment rapid pathologic evaluation of resected tissues in the age of digital pathology.

The Impact of On-Target Resistance Mediated by EGFR-T790M or EGFR-C797S on EGFR Exon 20 Insertion Mutation Active Tyrosine Kinase Inhibitors.

Introduction: Mechanisms of resistance to EGFR exon 20 insertion mutation active inhibitors have not been extensively studied in either robust preclinical models or patient-derived rebiopsy specimens. We sought to characterize on-target resistance mutations identified in EGFR exon 20 insertion-mutated lung cancers treated with mobocertinib or poziotinib and evaluate whether these mutations would or would not have cross-resistance to next-generation inhibitors zipalertinib, furmonertinib, and sunvozertinib. Methods: We identified mechanisms of resistance to EGFR exon 20 insertion mutation active inhibitors and then used preclinical models of EGFR exon 20 insertion mutations (A767_V769dupASV, D770_N771insSVD, V773_C774insH) plus common EGFR mutants to probe inhibitors in the absence/presence of EGFR-T790M or EGFR-C797S. Results: Mobocertinib had a favorable therapeutic window in relation to EGFR wild type for EGFR exon 20 insertion mutants, but the addition of EGFR-T790M or EGFR-C797S negated the observed window. Zipalertinib had a favorable therapeutic window for cells driven by EGFR-A767_V769dupASV or EGFR-D770_N771insSVD in the presence or absence of EGFR-T790M. Furmonertinib and sunvozertinib had the most favorable therapeutic windows in the presence or absence of EGFR-T790M in all cells tested. EGFR-C797S in cis to all EGFR mutations evaluated generated dependent cells that were resistant to the covalent EGFR tyrosine kinase inhibitors mobocertinib, zipalertinib, furmonertinib, sunvozertinib, poziotinib, and osimertinib. Conclusions: This report highlights that poziotinib and mobocertinib are susceptible to on-target resistance mediated by EGFR-T790M or -C797S in the background of the most prevalent EGFR exon 20 insertion mutations. Furmonertinib, sunvozertinib, and to a less extent zipalertinib can overcome EGFR-T790M compound mutants, whereas EGFR-C797S leads to covalent inhibitor cross-resistance-robust data that support the limitations of mobocertinib and should further spawn the development of next-generation covalent and reversible EGFR exon 20 insertion mutation active inhibitors with favorable therapeutic windows that are less vulnerable to on-target resistance.

A Real-World Study of Patient Characteristics and Clinical Outcomes in EGFR Mutated Lung Cancer Treated with First-Line Osimertinib: Expanding the FLAURA Trial Results into Routine Clinical Practice.

Osimertinib is a tyrosine kinase inhibitor of the epidermal growth factor receptor (EGFR) that is used for first-line therapy in EGFR mutated non-small cell lung cancer (NSCLC) based on the results of the randomized FLAURA trial (ClinicalTrials.gov number NCT02296125). We performed a retrospective analysis of baseline characteristics and clinical outcomes in 56 real-world patients treated with osimertinib. In total, 45% of patients were determined to be FLAURA-eligible and 55% were FLAURA-ineligible based on the published inclusion/exclusion criteria of the aforementioned trial. For clinical outcomes, the median osimertinib time to treatment discontinuation (TTD) for all patients was 16.9 months (95% CI: 12.6-35.1), whereas the median TTD was 31.1 months (95% CI: 14.9-not reached) in the FLAURA-eligible cohort and the median TTD was 12.2 months (95% CI: 8.1-34.6 months) in the FLAURA-ineligible cohort. Re-biopsy at acquired resistance disclosed both on- and off-target mechanisms. The most common therapies following osimertinib included local therapies followed by post-progression osimertinib, platinum-doublet chemotherapy with or without osimertinib, and osimertinib combinatory targeted therapies. The median overall survival for all patients was 32.0 months (95% CI: 15.7-not reached), the median survival was not reached for the FLAURA-eligible cohort, and it was 16.5 months for the FLAURA-ineligible cohort. Our data support the use of osimertinib in real-word settings and highlight the need for designing registration trials that are more inclusive of patient/disease characteristics seen in routine clinical practice. It is yet to be determined if the use of evolving first-line EGFR inhibitor combination strategies (either platinum-doublet chemotherapy plus osimertinib or amivantamab plus lazertinib) will similarly translate from clinical trials to real-word settings.