Deciphering cell states and genealogies of human haematopoiesis.

The human blood system is maintained through the differentiation and massive amplification of a limited number of long-lived haematopoietic stem cells (HSCs)1. Perturbations to this process underlie diverse diseases, but the clonal contributions to human haematopoiesis and how this changes with age remain incompletely understood. Although recent insights have emerged from barcoding studies in model systems2-5, simultaneous detection of cell states and phylogenies from natural barcodes in humans remains challenging. Here we introduce an improved, single-cell lineage-tracing system based on deep detection of naturally occurring mitochondrial DNA mutations with simultaneous readout of transcriptional states and chromatin accessibility. We use this system to define the clonal architecture of HSCs and map the physiological state and output of clones. We uncover functional heterogeneity in HSC clones, which is stable over months and manifests as both differences in total HSC output and biases towards the production of different mature cell types. We also find that the diversity of HSC clones decreases markedly with age, leading to an oligoclonal structure with multiple distinct clonal expansions. Our study thus provides a clonally resolved and cell-state-aware atlas of human haematopoiesis at single-cell resolution, showing an unappreciated functional diversity of human HSC clones and, more broadly, paving the way for refined studies of clonal dynamics across a range of tissues in human health and disease.

Single-Cell Transcriptomics of Human and Mouse Lung Cancers Reveals Conserved Myeloid Populations across Individuals and Species.

Tumor-infiltrating myeloid cells (TIMs) comprise monocytes, macrophages, dendritic cells, and neutrophils, and have emerged as key regulators of cancer growth. These cells can diversify into a spectrum of states, which might promote or limit tumor outgrowth but remain poorly understood. Here, we used single-cell RNA sequencing (scRNA-seq) to map TIMs in non-small-cell lung cancer patients. We uncovered 25 TIM states, most of which were reproducibly found across patients. To facilitate translational research of these populations, we also profiled TIMs in mice. In comparing TIMs across species, we identified a near-complete congruence of population structures among dendritic cells and monocytes; conserved neutrophil subsets; and species differences among macrophages. By contrast, myeloid cell population structures in patients' blood showed limited overlap with those of TIMs. This study determines the lung TIM landscape and sets the stage for future investigations into the potential of TIMs as immunotherapy targets.

Mesothelioma: Scientific clues for prevention, diagnosis, and therapy.

Mesothelioma affects mostly older individuals who have been occupationally exposed to asbestos. The global mesothelioma incidence and mortality rates are unknown, because data are not available from developing countries that continue to use large amounts of asbestos. The incidence rate of mesothelioma has decreased in Australia, the United States, and Western Europe, where the use of asbestos was banned or strictly regulated in the 1970s and 1980s, demonstrating the value of these preventive measures. However, in these same countries, the overall number of deaths from mesothelioma has not decreased as the size of the population and the percentage of old people have increased. Moreover, hotspots of mesothelioma may occur when carcinogenic fibers that are present in the environment are disturbed as rural areas are being developed. Novel immunohistochemical and molecular markers have improved the accuracy of diagnosis; however, about 14% (high-resource countries) to 50% (developing countries) of mesothelioma diagnoses are incorrect, resulting in inadequate treatment and complicating epidemiological studies. The discovery that germline BRCA1-asssociated protein 1 (BAP1) mutations cause mesothelioma and other cancers (BAP1 cancer syndrome) elucidated some of the key pathogenic mechanisms, and treatments targeting these molecular mechanisms and/or modulating the immune response are being tested. The role of surgery in pleural mesothelioma is controversial as it is difficult to predict who will benefit from aggressive management, even when local therapies are added to existing or novel systemic treatments. Treatment outcomes are improving, however, for peritoneal mesothelioma. Multidisciplinary international collaboration will be necessary to improve prevention, early detection, and treatment.

Contemporary issues in the surgical management of pleural mesothelioma.

The surgical management of pleural mesothelioma (PM) can be divided into diagnostic, staging, palliation, and cytoreductive surgery. In the cytoreductive surgical setting, the combination of different treatment modalities has led to better outcomes than surgery alone. The scarcity of high-quality studies has led to heterogeneity in management of PM across the mesothelioma treatment centers. Here, we review the literature regarding the most important open questions and ongoing clinical trials.

Hyperthermic intraoperative chemotherapy (HIOC) for Stage IVa thymic malignancy may improve 5-year disease-free survival.

BACKGROUND AND OBJECTIVES: Stage IVa thymic malignancy has limited treatments. This study evaluated whether hyperthermic intraoperative chemotherapy (HIOC) after radical resection of Stage IVa thymic malignancy improves survival. METHODS: All patients who underwent resection, with or without HIOC, for Stage IVa thymic malignancy at a single center from 1990 to 2021 were reviewed. RESULTS: Thirty-four patients were identified; 22 surgery-only versus 12 surgery and HIOC (60 min cisplatin regimen 175 mg/m2 ). Demographics and comorbidities were similar between groups. Three patients in each group were carcinomas; remainder were thymomas. Thirty-two patients underwent attempted macroscopic complete resection; 22 operations succeeded, 68.8%. Significant complications were similar between groups, 18.2% surgery-only versus 25.0% HIOC, p = 0.68. Median time to recurrence trended longer for HIOC patients (42.9 vs. 32.9 months in surgery-only, p = 0.77). Overall survival, 5-year, was similar (75.8% HIOC vs. 76.2% surgery-only, p = 0.91). On stratified analysis, thymoma patients with macroscopic complete resection and HIOC experienced similar 5-year Overall (80.0% vs. 100.0% surgery-only, p = 0.157) but longer trending 5-year disease-free (85.7% vs. 40.0%, p = 0.18) and 5-year locoregional recurrence-free survival (85.7% vs. 68.6%, p = 0.75). CONCLUSIONS: This retrospective cohort study treating Stage IVa thymic malignancy with radical pleurectomy, with or without HIOC, found addition of HIOC-signaled delayed recurrence and improved disease-free survival.

High-dose IV magnesium in mesothelioma patients receiving surgery with hyperthermic intraoperative cisplatin: Pilot studies and design of a phase II randomized clinical trial.

INTRODUCTION: Hyperthermic intraoperative cisplatin (HIOC) is associated with acute kidney injury (AKI). Administration of high-dose magnesium attenuates cisplatin-induced AKI (CP-AKI) in animal models but has not been rigorously examined in humans. METHODS: We tested the feasibility and safety of different doses of magnesium in mesothelioma patients receiving HIOC. In Pilot Study 1, we administered a 36-h continuous infusion of magnesium at 0.5 g/h, targeting serum magnesium levels between 3 and 4.8 mg/dL. In Pilot Study 2A, we administered a 6 g bolus followed by an infusion starting at 2 g/h, titrated to achieve levels between 4 and 6 mg/dL. We eliminated the bolus in Pilot Study 2B. RESULTS: In Pilot Study 1, all five patients enrolled completed the study; however, median postoperative Mg levels were only 2.4 mg/dL. In Pilot Study 2A, two of four patients (50%) were withdrawn due to bradycardia during the bolus. In Pilot Study 2B, two patients completed the study whereas two developed postoperative bradycardia attributed to the magnesium. CONCLUSIONS: A 0.5 g/h infusion for 36 h did not achieve therapeutic magnesium levels, while an infusion at 2 g/h was associated with bradycardia. These studies informed the design of a randomized clinical trial testing whether intravenously Mg attenuates HIOC-associated AKI.

Identifying chronic obstructive pulmonary disease from integrative omics and clustering in lung tissue.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a highly morbid and heterogenous disease. While COPD is defined by spirometry, many COPD characteristics are seen in cigarette smokers with normal spirometry. The extent to which COPD and COPD heterogeneity is captured in omics of lung tissue is not known. METHODS: We clustered gene expression and methylation data in 78 lung tissue samples from former smokers with normal lung function or severe COPD. We applied two integrative omics clustering methods: (1) Similarity Network Fusion (SNF) and (2) Entropy-Based Consensus Clustering (ECC). RESULTS: SNF clusters were not significantly different by the percentage of COPD cases (48.8% vs. 68.6%, p = 0.13), though were different according to median forced expiratory volume in one second (FEV1) % predicted (82 vs. 31, p = 0.017). In contrast, the ECC clusters showed stronger evidence of separation by COPD case status (48.2% vs. 81.8%, p = 0.013) and similar stratification by median FEV1% predicted (82 vs. 30.5, p = 0.0059). ECC clusters using both gene expression and methylation were identical to the ECC clustering solution generated using methylation data alone. Both methods selected clusters with differentially expressed transcripts enriched for interleukin signaling and immunoregulatory interactions between lymphoid and non-lymphoid cells. CONCLUSIONS: Unsupervised clustering analysis from integrated gene expression and methylation data in lung tissue resulted in clusters with modest concordance with COPD, though were enriched in pathways potentially contributing to COPD-related pathology and heterogeneity.

Pleurectomy Decortication in the Treatment of Malignant Pleural Mesothelioma: Encouraging Results and Novel Prognostic Implications Based on Experience in 355 Consecutive Patients.

OBJECTIVE: We report a series of 355 consecutive patients treated over 9 years in a single institution with intended PDC. BACKGROUND: Surgery for MPM has shifted from extra-pleural pneumonectomy to PDC with the goal of MCR. METHODS: Clinical and outcome data were reviewed. Kaplan-Meier estimators and log rank test were used to compare the overall survival, and logistic regression models were used. RESULTS: MCR was achieved in 304. There were 223 males, median age was 69 and histology was epithelioid in 184. The 30 and 90-day mortality were 3.0% and 4.6%.Most complications were low grade. Prolonged air leak in 141, deep venous thrombosis in 64, Atrial fibrillation in 42, chylothorax in 24, Empyema in 23, pneumonia in 21, Hemothorax in 12 and pulmonary embolus in 8. Median/5-year survival were 20.7 months/17.9% in the intent-to-treat cohort and 23.2months/21.2% in the MCR group. The survivals were best for patients with Tlstage and epithelioid histology (69.8months/54.1%). In a multivariable analysis, factors that were found to be associated with longer patient overall survival included epithelioid histology, T stage, quantitative clinical stage/tumor volume staging, adjuvant chemotherapy, intraoperative heated chemo, female sex, and length of stay shorter than 14 days. CONCLUSIONS: PDC is feasible with low mortality and is associated with manageable complication rates. 5-year survival of patients undergoing PDC with MCR in multi-modality setting is approaching 25% depending on quantitative and clinical stage, sex and histological subtype and is better than PDC without- MCR.

Clinical and molecular validation of BAP1, MTAP, P53, and Merlin immunohistochemistry in diagnosis of pleural mesothelioma.

BAP1 and MTAP immunostains play an important role in diagnosis of mesothelioma, but additional markers are needed to increase sensitivity. We analyzed 84 pleural mesotheliomas (51 epithelioid, 27 biphasic, 6 sarcomatoid) by a hybrid-capture next-generation sequencing (NGS) panel including complete coverage of coding and splicing regions for BAP1, CDKN2A/MTAP, NF2, and TP53 and correlated molecular findings with diagnostic immunostains for BAP1, MTAP, Merlin, and p53, respectively. Fifty-seven reactive mesothelial proliferations served as benign comparators. Loss of BAP1, MTAP, and Merlin protein expression were, respectively, 54%, 46%, and 52% sensitive and 100% specific for mesothelioma. Two-marker immunopanels of BAP1 + MTAP, BAP1 + Merlin, and MTAP + Merlin were 79%, 85%, and 71% sensitive for mesothelioma, while a three-marker immunopanel of BAP1 + MTAP + Merlin was 90% sensitive. Diffuse (mutant-pattern) p53 immunostaining was seen in only 6 (7%) tumors but represented the only immunohistochemical abnormality in 2 cases. Null-pattern p53 was not specific for malignancy. An immunopanel of BAP1 + MTAP + Merlin + p53 was 93% sensitive for mesothelioma, and panel NGS detected a pathogenic alteration in BAP1, MTAP, NF2, and/or TP53 in 95%. Together, 83 (99%) of 84 tumors showed a diagnostic alteration by either immunohistochemistry or panel NGS. Adding Merlin to the standard BAP1 + MTAP immunopanel increases sensitivity for mesothelioma without sacrificing specificity. p53 immunohistochemistry and panel NGS with complete coverage of BAP1, CDKN2A/MTAP, TP53, and NF2 may be useful in diagnostically challenging cases.

Salvage surgery for local recurrence after sublobar surgery in Stages I and II non-small cell lung cancer.

BACKGROUND AND OBJECTIVES: To examine if patients undergoing salvage surgery for local recurrence following sublobar resection (SLR) have similar perioperative complications and overall survival (OS) compared to lobectomy patients for early stage non-small cell lung cancer (NSCLC). METHODS: Patients undergoing lobectomy and SLR (segmentectomy or wedge resection) for Stages I and II NSCLC from 2010 to 2016 were reviewed. Lobectomy patients and those who underwent salvage surgery for local recurrence after SLR were compared. Salvage surgeries were curative-intent resections for recurrence. RESULTS: Cases included 634 lobectomies and 986 SLR. Fifty-nine SLR patients (6.0%) recurred at a local site compared to 11 lobectomy patients (1.7%; p < 0.001). Twenty-three locally recurrent SLR patients (39.0%) went on to salvage surgery. Peri-operative complications after salvage surgeries were similar to lobectomies (34.8% 8/23 vs. 34.7% 220/634, p = 1.00). OS at 5 years for salvage surgery patients was similar to lobectomy patients (79.6% 13/23 vs. 70.6% 227/634, p = 0.23). OS for patients who underwent salvage surgery was significantly better than those who did not have salvage surgery for recurrence (79.6% vs. 53.0%, p = 0.02). CONCLUSIONS: Patients who undergo salvage surgery for local recurrence after SLR had similar perioperative complications and OS compared to lobectomy patients but less than half underwent salvage surgery.

Large-scale analysis of BAP1 expression reveals novel associations with clinical and molecular features of malignant pleural mesothelioma.

BRCA1-associated protein-1 (BAP1) expression is commonly lost in several tumors including malignant pleural mesothelioma (MPM). Presence or absence of immunohistochemical BAP1 nuclear staining in tumor cells is currently used for differential diagnosis of MPM. In this study, a large cohort of 596 MPM tumors with available clinical data was analyzed to examine associations of BAP1 staining pattern with clinical and molecular features that may reflect the impact of BAP1 mutation on MPM biology. Cases were classified according to the BAP1 staining pattern of tumor cells. Exome and RNA-sequencing data were available for subsets of cases. Levels of mRNA encoding claudin 15 (CLDN15) and vimentin (VIM) were determined using RT-qPCR on 483 cases to estimate the relative proportions of epithelial-like and mesenchymal-like components in each tumor. Four BAP1 staining patterns were observed: single-pattern nuclear staining (36%), single-pattern cytoplasmic staining (25%), single-pattern absent staining (12%), and combinations of these staining patterns (27%). This study confirmed prior reports that nuclear BAP1 is more frequently associated with wild-type BAP1 and sarcomatoid histology. However, no associations between BAP1 staining pattern(s) and mutations in specific protein domains and/or mutation type were observed. BAP1 staining patterns were significantly associated (p < 0.001) with BAP1 gene expression, MPM histologic subtypes, molecular clusters, and markers of epithelial-to-mesenchymal transition. Frequent observation of combinations of BAP1 staining patterns in MPM tumors indicated intra-tumoral heterogeneity of BAP1 status. Cytoplasmic BAP1 staining was identified as a putative indicator of favorable prognosis in non-epithelioid MPM. In conclusion, novel significant associations among different BAP1 staining patterns and subgroups of MPM tumors were observed, suggesting that the role of BAP1 in tumor progression may be more complex than its presumed tumor suppressor function. Cytoplasmic staining was identified as a putative indicator of favorable prognosis in non-epithelioid MPM, potentially addressing a critical need in clinical decision-making in this disease. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

The Rocky Road from Preclinical Findings to Successful Targeted Therapy in Pleural Mesothelioma.

Pleural mesothelioma (PM) is a rare and aggressive disease that arises from the mesothelial cells lining the pleural cavity. Approximately 80% of PM patients have a history of asbestos exposure. The long latency period of 20-40 years from the time of asbestos exposure to diagnosis, suggests that multiple somatic genetic alterations are required for the tumorigenesis of PM. The genomic landscape of PM has been characterized by inter- and intratumor heterogeneity associated with the impairment of tumor suppressor genes such as CDKN2A, NF2, and BAP1. Current systemic therapies have shown only limited efficacy, and none is approved for patients with relapsed PM. Advances in understanding of the molecular landscape of PM has facilitated several biomarker-driven clinical trials but so far, no predictive biomarkers for targeted therapies are in clinical use. Recent advances in the PM genetics have provided optimism for successful molecular strategies in the future. Here, we summarize the molecular mechanism underlying PM pathogenesis and review potential therapeutic targets.

Lung proteomic biomarkers associated with chronic obstructive pulmonary disease.

Identifying protein biomarkers for chronic obstructive pulmonary disease (COPD) has been challenging. Most previous studies have used individual proteins or preselected protein panels measured in blood samples. Mass spectrometry proteomic studies of lung tissue have been based on small sample sizes. We used mass spectrometry proteomic approaches to discover protein biomarkers from 150 lung tissue samples representing COPD cases and controls. Top COPD-associated proteins were identified based on multiple linear regression analysis with false discovery rate (FDR) < 0.05. Correlations between pairs of COPD-associated proteins were examined. Machine learning models were also evaluated to identify potential combinations of protein biomarkers related to COPD. We identified 4,407 proteins passing quality controls. Twenty-five proteins were significantly associated with COPD at FDR < 0.05, including interleukin 33, ferritin (light chain and heavy chain), and two proteins related to caveolae (CAV1 and CAVIN1). Multiple previously reported plasma protein biomarkers for COPD were not significantly associated with proteomic analysis of COPD in lung tissue, although RAGE was borderline significant. Eleven pairs of top significant proteins were highly correlated (r > 0.8), including several strongly correlated with RAGE (EHD2 and CAVIN1). Machine learning models using Random Forests with the top 5% of protein biomarkers demonstrated reasonable accuracy (0.707) and area under the curve (0.714) for COPD prediction. Mass spectrometry-based proteomic analysis of lung tissue is a promising approach for the identification of biomarkers for COPD.

Essential role of the histone lysine demethylase KDM4A in the biology of malignant pleural mesothelioma (MPM).

BACKGROUND: Malignant pleural mesothelioma (MPM) is a highly aggressive cancer with a dismal prognosis. There is increasing interest in targeting chromatin regulatory pathways in difficult-to-treat cancers. In preliminary studies, we found that KDM4A (lysine-specific histone demethylase 4) was overexpressed in MPM. METHODS: KDM4A protein expression was determined by immunohistochemistry or immunoblotting. Functional inhibition of KDM4A by targeted knockdown and small molecule drugs was correlated to cell growth using cell lines and a xenograft mouse model. Gene expression profiling was performed to identify KDM4A-dependent signature pathways. RESULTS: Levels of KDM4A were found to be significantly elevated in MPM patients compared to normal mesothelial tissue. Inhibiting the enzyme activity efficiently reduced cell growth in vitro and reduced tumour growth in vivo. KDM4A inhibitor-induced apoptosis was further enhanced by the BH3 mimetic navitoclax. KDM4A expression was associated with pathways involved in cell growth and DNA repair. Interestingly, inhibitors of the DNA damage and replication checkpoint regulators CHK1 (prexasertib) and WEE1 (adavosertib) within the DNA double-strand break repair pathway, cooperated in the inhibition of cell growth. CONCLUSIONS: The results establish a novel and essential role for KDM4A in growth in preclinical models of MPM and identify potential therapeutic approaches to target KDM4A-dependent vulnerabilities.

Adjuvant therapy following induction therapy and surgery improves survival in N2-positive non-small cell lung cancer.

BACKGROUND: The purpose of this study was to evaluate treatment strategies and factors influencing overall survival (OS) and disease-free survival (DFS) in resectable, non-small cell lung cancer (NSCLC) with mediastinal (N2) lymph node metastasis. METHODS: All patients undergoing surgery for NSCLC with N2 disease between 2006 and 2016 were included. Treatment approaches included surgery only, neoadjuvant therapy followed by surgery, surgery followed by adjuvant therapy, and neoadjuvant therapy followed by surgery and adjuvant therapy (triple therapy). Patient clinical and pathologic data were retrospectively collected. RESULTS: A total of 281 patients were included in the study. In total, 209 patients had neoadjuvant therapy, 47.4% of which went on to received additional adjuvant therapy. The pathologic complete response rate was 12.9%. The treatment strategy which included triple therapy was isolated as a significant contributor to improved OS and DFS. Nodal downstaging (N0) after induction therapy conferred an OS benefit (38.3% vs. 15.6%, p = .03). Patients with single-station N2 disease experienced higher DFS. Video-assisted thoracic surgery (VATS) lobectomy completion rates were higher at the end of the study period compared to the beginning (p < .001). CONCLUSIONS: Patients who undergo neoadjuvant therapy for N2-positive NSCLC may benefit from additional adjuvant therapy. Single-station N2 disease confers higher DFS. VATS completion rates for lobectomy increase as experience increases.

Outcomes of superior segmentectomy versus lower lobectomy for superior segment Stage I non-small-cell lung cancer are equivalent: An analysis of 196 patients at a single, high volume institution.

OBJECTIVES: To determine if superior segmentectomy has equivalent overall (OS), disease-free (DFS), and locoregional-recurrence-free survival (LRFS) to lower lobectomy for early-stage non-small-cell lung cancer (NSCLC) in the superior segment. METHODS: We retrospectively reviewed all Stage 1 lower lobectomies for superior segment lesions and superior segmentectomies at our hospital from 2000 to 2018. Comparison statistics and Cox hazard modeling were performed to determine differences between groups and attempt to identify risk factors for OS, DFS, and LRFS. RESULTS: Superior segmentectomy patients, compared with lower lobectomy patients, had more current smokers, worse forced expiratory volume in 1 s percentage, radiologic emphysema scores, clinically and pathologically smaller tumors, and more occurrences of 0 lymph nodes examined. Outcomes for superior segmentectomy compared with lower lobectomy were equivalent for 5-year OS (67.0% vs. 75.1%, p = 0.70), DFS (56.9% vs. 60.4%, p = 0.59), and LRFS (87.9% vs. 91.3%, p = 0.46). Multivariable Cox modeling lacked utility due to no outcome differences. CONCLUSIONS: In well-selected patients, superior segmentectomies can have equivalent OS, DFS, and LRFS compared with lower lobectomies of superior segment tumors for early stage lung cancer. Further data are needed to provide better risk estimates.

Long-Term Radiologic Evaluation of Microaspirations among Patients after Esophagectomy.

OBJECTIVES: Aspirations are common after esophagectomy. Data are lacking regarding its long-term radiological manifestations. The purpose of this study is to determine the incidence and radiological patterns of aspirations among long-term survivors and evaluate their clinical significance. METHODS: The records of all patients who underwent esophagectomy between October 2003 and December 2011 and survived more than 3 years were reviewed. Preoperative, first routine postoperative, and latest chest computed tomography (CT)scans were reviewed. Imaging studies were reviewed for radiological signs suspicious of aspirations, conduit location, anastomotic site, and maximal intrathoracic diameter. Data regarding patients' complaints during clinic visits were also collected. RESULTS: A total of 578 patients underwent esophagectomy during the study period. One-hundred twenty patients met the inclusion criteria. Median follow-up was 83.5 months. Cervical and intrathoracic anastomoses were performed in 103 and 17 patients, respectively. A higher rate of CT findings was found in postoperative imaging (n = 51 [42.5%] vs. n = 13 [10.8%] respectively, p < 0.05). Most of these were found in the lower lobes (61%). A higher rate of lesions was found among patients in whom the conduit was bulging to the right hemithorax compared with totally mediastinal or completely in the right hemithorax (54.5 vs. 35.2% and 34.6%, respectively, p < 0.05). No correlation was found with conduit diameter or anastomotic site. These lesions were more prevalent among patients who complained of reflux or cough during meals (NS). CONCLUSIONS: A significantly higher rate of new CT findings was found in postoperative imaging of this post-esophagectomy cohort, suggesting a high incidence of aspirations. The locations of the conduit, rather than anastomosis site, seem to play a role in the development of these findings. Further research is needed to evaluate the clinical significance of these findings.

Molecular characterization of diffuse malignant peritoneal mesothelioma.

Malignant peritoneal mesothelioma is a rare aggressive tumor that arises from the peritoneal lining. While recurrent BAP1 mutations have been identified in a subset of mesotheliomas, molecular characteristics of peritoneal mesotheliomas, including those lacking BAP1 alterations, remain poorly understood. Using targeted next-generation sequencing, we examined the molecular features of 26 diffuse malignant peritoneal mesotheliomas. As part of an exploratory analysis, we analyzed an additional localized peritoneal mesothelioma and one well-differentiated papillary mesothelioma with invasive foci. Genomic characterization identified categories of diffuse malignant peritoneal mesotheliomas: The first group included 18 (69%) tumors with recurrent BAP1 alterations, with eight (31%) having more than one BAP1 alterations, and concomitant alterations in PBRM1 (46%) and SETD2 (35%). All tumors with complete loss of BAP1 expression by immunohistochemistry harbored BAP1 molecular alterations. PBRM1 alterations were significantly enriched in the BAP1-altered cohort. Frequent copy number loss of BAP1, ARID1B, PRDM1, PBRM1, SETD2, NF2, and CDKN2A was noted. The second group included eight (31%) BAP1-wild-type tumors: two with TP53 mutations, one with a TRAF7 activating mutation, one with a SUZ12 inactivating mutation, and three with ALK rearrangements that we previously published. One TP53-mutant biphasic mesothelioma showed evidence of genomic near-haploidization showing loss of heterozygosity of all chromosomes except 5, 7, 16, and 20. The localized peritoneal mesothelioma harbored a nonsense CHEK2 mutation, and the well-differentiated papillary mesothelioma with invasive foci harbored no reportable variants. In conclusion, we described the genetic categories of diffuse malignant peritoneal mesotheliomas, with BAP1-mutant and BAP1-wild-type groups. Our findings implicated DNA repair, epigenetics, and cell cycle regulation in the pathogenesis of peritoneal mesotheliomas, with identification of potential therapeutic targets.

Molecular characterization of localized pleural mesothelioma.

Localized pleural mesothelioma is a rare solitary circumscribed pleural tumor that is microscopically similar to diffuse malignant pleural mesothelioma. However, the molecular characteristics and nosologic relationship with its diffuse counterpart remain unknown. In a consecutive cohort of 1110 patients with pleural mesotheliomas diagnosed in 2005-2018, we identified six (0.5%) patients diagnosed with localized pleural mesotheliomas. We gathered clinical history, evaluated the histopathology, and in select cases performed karyotypic analysis and targeted next-generation sequencing. The cohort included three women and three men (median age 63; range 28-76), often presenting incidentally during radiologic evaluation for unrelated conditions. Neoadjuvant chemotherapy was administered in two patients. All tumors (median size 5.0 cm; range 2.7-13.5 cm) demonstrated gross circumscription (with microscopic invasion into lung, soft tissue, and/or rib in four cases), mesothelioma histology (four biphasic and two epithelioid types), and mesothelial immunophenotype. Of four patients with at least 6-month follow-up, three were alive (up to 8.9 years). Genomic characterization identified several subgroups: (1) BAP1 mutations with deletions of CDKN2A and NF2 in two tumors; (2) TRAF7 mutations in two tumors, including one harboring trisomies of chromosomes 3, 5, 7, and X; and (3) genomic near-haploidization, characterized by extensive loss of heterozygosity sparing chromosomes 5 and 7. Localized pleural mesotheliomas appear genetically heterogeneous and include BAP1-mutated, TRAF7-mutated, and near-haploid subgroups. While the BAP1-mutated subgroup is similar to diffuse malignant pleural mesotheliomas, the TRAF7-mutated subgroup overlaps genetically with adenomatoid tumors and well-differentiated papillary mesotheliomas, in which recurrent TRAF7 mutations have been described. Genomic near-haploidization, identified recently in a subset of diffuse malignant pleural mesotheliomas, suggests a novel mechanism in the pathogenesis of both localized pleural mesothelioma and diffuse malignant pleural mesothelioma. Our findings describe distinctive genetic features of localized pleural mesothelioma, with both similarities to and differences from diffuse malignant pleural mesothelioma.

Image-guided video-assisted thoracoscopic resection (iVATS): Translation to clinical practice-real-world experience.

OBJECTIVE: We developed a novel approach for localization and resection of lung nodules, using image-guided video-assisted thoracoscopic surgery (iVATS). We report our experience of translating iVATS into clinical care. METHODS: Methodology and workflow for iVATS developed as part of the Phase I/II trial were used to train surgeons, radiologists, anesthesiologists, and radiology technologists. Radiation dose, time from induction to incision, placement of T-bar to incision and incision to closure, hospital stay, and complication rates were recorded. RESULTS: Fifty patients underwent iVATS for resection of 54 nodules in a clinical hybrid operating room (OR) by six surgeons. Fifty-two (97%) nodules were successfully resected. Forty-two (84%) patients underwent wedge resection, four (7%) lobectomies, and two (4%) segmentectomy all with lymph node dissection. Median time from induction to incision was 89 minutes (range: 13-256 minutes); T-bar placement was 14 minutes (10-29 minutes); and incision to closure, 107 minutes (41-302 minutes). Average and total procedure radiation dose were: median = 6 mSieverts (range: 2.9-35 mSieverts). No deaths were reported and median length of stay was 3 days (range: 1-12 days). CONCLUSIONS: Translation of iVATS into clinical practice has been initiated using a safe step-wise process, combining intraoperative C-arm computed tomography scanning and thoracoscopic surgery in a hybrid OR.