Die Aktualisierung der American Thoracic Society/European Respiratory Society(ATS/ERS)-Klassifikation der interstitiellen Pneumonien von 2025 erweitert deren Einteilung über rein idiopathische Entitäten hinaus und umfasst nun auch Krankheitsbilder mit identifizierbaren Auslösern [1]. Zentraler Bestandteil dieser Aktualisierung ist die terminologische Neuausrichtung der Klassifikation zu einem deskriptiven, primär morphologisch orientierten Konzept mit dem Ziel der klaren Unterscheidung von radiologischen und histologischen Mustern auf der einen und von klinisch definierten Erkrankungen auf der anderen Seite. Die akute interstitielle Pneumonie (AIP) wird nun als idiopathische diffuse alveoläre Schädigung (DAD) bezeichnet, die desquamative interstitielle Pneumonie (DIP) als Alveolarmakrophagenpneumonie (AMP). Das Muster der bronchiolozentrischen interstitiellen Pneumonie (BIP) wird als eigenständiges morphologisches Muster eingeführt, der Begriff der Hypersensitivitätspneumonitis (HP) soll künftig ausschließlich der multidisziplinären Diagnose vorbehalten sein. Darüber hinaus bietet die aktualisierte Klassifikation ein biologisch begründetes und klinisch anwendbares System zur Kategorisierung in interstitielle und alveoläre Füllmuster und die auch prognostisch relevante Aufteilung in fibrotische und nichtfibrotische Verläufe. Hervorzuheben ist zudem eine stärkere Betonung der transparenten Angabe der diagnostischen Sicherheit im interdisziplinären Board für interstitielle Lungenerkrankungen (ILD-Board), inklusive der Vergabe von „provisorischen“ Diagnosen bzw. Verwendung des Begriffs der „unklassifizierbaren ILD“ bei niedriger und sehr niedriger diagnostischer Sicherheit. Die aktuelle Klassifikation kann helfen, den diagnostischen Ablauf und den Entscheidungsprozess im ILD-Board zu standardisieren und transparenter zu gestalten und dadurch auch die klinische Versorgung zu optimieren. Es ist zu erwarten, dass dieses Update die Grundlage für künftige Forschung und neue Erkenntnisse im Bereich der ILD sein wird. Daneben soll jedoch nicht unerwähnt bleiben, dass die neue Klassifikation hinsichtlich der Einführung des Musters der BIP und der provisorischen Entität der „idiopathischen BIP“ von einigen ExpertInnen kritisch beurteilt wird. Befürchtet wird konkret, dass durch die stärkere Betonung eines morphologischen Musters und die terminologische Abgrenzung zur HP die diagnostische Aufmerksamkeit für potenziell auslösende Expositionen abgeschwächt werden könnte.

Diffuse mesothelioma is typically diagnosed through histopathologic evaluation. Recent advances in therapeutic strategies have heightened the importance of accurate diagnosis and subtyping. In addition to the three well-established histologic subtypes of mesothelioma (epithelioid, biphasic, and sarcomatoid), the 2021 WHO classification of diffuse pleural mesothelioma emphasizes the importance of subtyping patterns and cytologic features to improve clinical diagnosis and patient management. Notably, the presence of a solid component or pleomorphic cytologic features observed within the epithelioid subtype is associated with a worse prognosis, approaching that of sarcomatoid mesothelioma. Conversely, cases with abundant myxoid stroma and a solid component comprising less than 50% are associated with improved survival. In addition, a two-tiered grading system (low versus high grade) is now recommended for epithelioid mesothelioma. On behalf of the International Association for the Study of Lung Cancer Mesothelioma Sub-Committee of the Rare Tumor Group, we here outline new, essential elements to assist clinicians in optimizing the management of patients with mesothelioma. This includes practical questions on immunohistochemical and molecular markers BAP1, methylthioadenosine phosphorylase, NF2, and fusion genes that are relevant to the diagnosis, prognosis, and application of emerging therapeutic strategies in diffuse pleural mesothelioma. This discussion also addresses frequently asked questions by clinicians regarding sampling modalities aimed at optimizing diagnostic accuracy. The impact of epigenetics, DNA methylation, and biomarker discovery is highlighted, with an emphasis on its limitations in distinguishing mesothelioma from reactive mesothelial proliferations and other neoplastic mimics. The emerging role of artificial intelligence in subtyping, grading, and prediction of biomarkers for genomic subtyping is also discussed.

Despite recent advances in the treatment of pleural mesothelioma, it remains a challenging and heterogeneous disease, with limited options for patients. Survival rates have only marginally improved in the past years, highlighting the need for a better biological understanding of the disease for the translation into clinical practice. Although recent years have seen substantial progress in genomics and molecular pathology, much of the existing literature has focused on morphology-correlated changes, with molecular, immunohistochemical, clinical, and blood biomarkers largely studied in a correlative framework. Despite these efforts, TNM classification remains the most powerful predictor of survival and one of the most important parameters to guide therapy in clinical practice. However, emerging evidence reveals that histology alone fails to capture the full heterogeneity of the disease, leading to suboptimal diagnostic, prognostic, and therapeutic approaches. This review summarizes recent major molecular findings relating not only to histology but also ploidy, tumor microenvironment, and methylation—which together offer a more comprehensive understanding of interpatient heterogeneity. In light of these results, we discuss the potential for a new morpho-molecular classification based on these molecular findings to overcome the current clinical challenges. Future directions for the field are also proposed, including the potential for emerging technologies such as single-cell, spatial omics, and artificial intelligence to fill in the gaps of bulk studies and unveil clinically relevant information about pleural mesothelioma tumor heterogeneity.

INTRODUCTION:Mucin-producing lung adenocarcinoma is a distinct pathological subset, but its prognostic significance, particularly in relation to spread through air spaces (STAS), remains unclear. We used a study-specific analytic framework to separate mucin-producing adenocarcinomas into invasive mucinous adenocarcinoma (IMA) and invasive adenocarcinoma with extracellular mucin production (IAEM), and evaluated their clinicopathological features, prognosis, and the impact of STAS in a multinational cohort. METHODS:A total of 647 surgically resected primary lung adenocarcinomas from five countries were retrospectively analyzed. Histologic subtyping and STAS assessment were performed by expert pathologists using whole-slide images. Survival was evaluated by Kaplan-Meier analysis and log-rank testing. Exploratory RNA sequencing was performed in a subset of IMA cases. RESULTS:Mucin production was observed in 203 cases (31.4%). In univariable analysis, mucin-producing adenocarcinomas showed significantly worse overall survival (OS) than non-mucin-producing tumors; however, mucin status was not independently prognostic in multivariable analysis after adjustment for STAS and pathological stage. STAS was present in 302 cases (46.7%) and was associated with worse OS in all cohorts except Brazil. Mucin-producing adenocarcinomas without STAS showed better outcomes, and no deaths were observed in the small subgroup of STAS-negative IMA in this cohort. RNA sequencing suggested enrichment of gene expression profiles related to gastrointestinal epithelial cell types in IMA. CONCLUSIONS:Across five international cohorts, STAS was associated with adverse prognosis in lung adenocarcinoma, independent of mucin production. In this cohort, STAS-negative IMA was associated with favorable outcomes, suggesting that STAS may refine prognostic stratification in mucin-producing adenocarcinomas.

BACKGROUND: Glucose is an important fuel in cancer cells, however, its availability may be limited in solid tumors. Cell-autonomous, metabolic adaptations of cancer cells and non-malignant cells to glucose deprivation are still incompletely understood. METHODS: Here, we addressed the changes in central carbon metabolism in lung cancer cells and normal lung cells facing glucose limitation using stable isotopic labeling followed by nuclear magnetic resonance spectroscopy and mass spectrometry. RESULTS: Elevated levels and the release of newly synthesized aspartate were among the most prominent changes in low compared to high glucose conditions. The low glucose-induced export of aspartate occurred in different lung cancer cell lines, but also bronchial epithelial cells and cancer-associated fibroblasts. It was accompanied by a reduced use of aspartate in purine synthesis and suppressed by hypoxia. A knockout of the malate-aspartate shuttle (MAS) enzyme mitochondrial aspartate aminotransferase (GOT2) decreased aspartate release. Low glucose conditions diminished reduced nicotinamide adenine dinucleotide (NADH) and restoring NADH reversed aspartate synthesis, suggesting that the distal, NADH-dependent arm of the MAS is compromised under glucose deprivation. CONCLUSIONS: Cells accumulate and release aspartate, a biosynthetic precursor and signaling molecule, under low glucose conditions, largely due to a truncated MAS, as part of their adaptive metabolic response.

Background Hypersensitivity pneumonitis (HP) is characterized by a complex immunological reaction of the lung that may lead to chronic interstitial lung disease (ILD). Pulmonary hypertension (PH) may aggravate the clinical picture. We aimed to assess the prevalence of PH in two independent cohorts including patients with moderate and severe HP. Patients and Methods We retrospectively analyzed the data of HP patients with severe ILD undergoing lung transplantation (cohort-1) and invited HP patients with mild disease participating at pulmonary rehabilitation for a prospective screening for PH (cohort-2). The presence of PH was assessed by both echocardiography and right heart catheterization (RHC). Results In cohort 1 (n = 55, median age 57 [95% CI 52-60] years, 59% male, forced vital capacity [FVC] 37 [35-45] % predicted), echocardiographic systolic pulmonary arterial pressure (sPAP) was available in 31 patients and showed elevated values (53 [45-63] mmHg). Sixteen patients (29%) had a high probability of pulmonary hypertension (PH; sPAP > 50 mmHg). Based on clinical assessment, a non-invasive evaluation using echocardiography was performed in accordance with current guideline recommendations, followed by invasive assessment with right heart catheterization (RHC) in selected patients. RHC was performed in 21 patients, revealing a mean pulmonary arterial pressure (mPAP) of 28 (24-33) mmHg and a pulmonary vascular resistance (PVR) of 2.8 (2.2-3.4) Wood units; PH was confirmed in 15 patients (71% of those undergoing RHC, 27% of the total cohort). In cohort 2 (n = 96, median age 62 [60-65] years, 66% male, FVC 98 [95-104] % predicted), echocardiographic screening was available in 88 patients and showed upper-normal sPAP values (29 [28-31] mmHg). One patient (1%) had a high probability of PH. Following clinical assessment and guideline-recommended non-invasive screening, RHC was performed in 13 patients with suspected PH. Hemodynamic measurements showed an mPAP of 19 (16-21) mmHg and a PVR of 1.9 (1.7-2.8) Wood units; PH was confirmed in 5 patients (38% of those undergoing RHC, 5% of the total cohort). All five patients had a plausible alternative explanation for their PH. Conclusion PH is a frequent complication in patients with HP and severe ILD. In HP patients with mild disease, PH is uncommon and alternative causes should be considered.

Lung neuroendocrine tumours (NETs, also known as carcinoids) are rapidly rising in incidence worldwide but have unknown aetiology and limited therapeutic options beyond surgery. The current WHO classification, based on mitotic count and presence or absence of necrosis, divides lung NETs into grade-1 typical, and grade-2 atypical tumours. This dichotomous classification however does not account for recently described molecular entities nor is it sufficient for clinical management. Here we conducted integrative multi‐omic analyses on over 300 lung NETs including whole‐genome sequencing, transcriptome profiling, and DNA methylation arrays, followed by archetype analysis, to identify and characterise molecular groups. We further investigated molecular groups using spatial RNA sequencing and proteomics, and deep learning analysis of whole slide images. The integration of multi-omic data provided definitive proof of the existence of four strikingly different molecular groups that vary in patient characteristics, genomic and transcriptomic profiles, microenvironment, and morphology. Among these, we identified a new molecular group, enriched for highly aggressive supra‐carcinoids that displayed an immune‐rich microenvironment linked to tumour-macrophage crosstalk. We uncovered an undifferentiated cell population within supra-carcinoids and show the transcriptomic similarities between supra-carcinoids and the recently identified atypical small cell lung cancer tumours, further demonstrating their molecular link to high-grade lung neuroendocrine carcinomas. Multi-regional genomic analyses identified distinct evolutionary trajectories, suggesting that molecular groups are determined early in tumourigenesis by genomic events, and that transitions between groups, though infrequent, are possible for supra-carcinoids. Deep learning models accurately identified these groups based on morphology alone, outperforming current histological criteria. Together with the validation of a panel of immunohistochemistry markers, we demonstrated that these molecular groups can be accurately identified based on morphological features, facilitating their future implementation in the clinical setting. Our proposed morpho-molecular classification highlights potential group-specific therapeutic opportunities, with differences in expression to DLL3, EGFR, FGFR and TERT inhibitor targets. Overall, our findings unify previously proposed molecular classifications and refine the lung cancer map by revealing novel tumour phenotypes with potential implications for prognosis and therapeutic management.

Lung is a common site of metastasis for squamous cell carcinoma (SqCC), and distinguishing primary lung SqCC from pulmonary metastatic SqCC is critical for clinical decision-making, including treatment planning. However, no practical histological criteria have been established for routine diagnosis. This study aimed to develop histopathological criteria to differentiate lung SqCC and pulmonary metastatic SqCC. A total of 85 surgical cases (48 primary and 37 metastatic) were collected with clinical background data. Seven histological features were evaluated. Six [morphological heterogeneity, dilated airway, interstitial fibrosis (IF), squamous dysplasia (SD), emphysema, RB macrophage] were presented as primary-associated features, while stromal infarction was proposed as metastatic. Seven pathologists scored these features. Primary-associated findings showed significantly higher score in primary cases. Tumor size (size) was significantly larger in the primary group (median: primary, 30 mm; metastatic, 14 mm; p < 0.001). A multivariate analysis incorporating size produced the "pathological primary formula" based on parameter estimates: 0.70・IF + 0.36・SD + 0.09・size, with an AUC of 0.86, sensitivity of 89.5%, and specificity of 70.2%. These results suggest that the extracted histologic features may provide reproducible criteria for distinguishing primary lung SqCC from pulmonary metastatic SqCC, offering insight into potential diagnostic applications.

Intraoperative frozen section diagnostics remains the standard for surgical margin assessment in oncologic surgery but is limited by interobserver variability, restricted availability, and time constraints. Optical emission spectroscopy (OES), a label-free analytical technique, offers a potential alternative by utilizing emission spectra generated during radiofrequency (RF) ablation to distinguish normal from malignant tissues. In this ambispective, multicenter feasibility study, OES spectra were recorded from 137 liver specimens (fresh and cryopreserved) obtained from patients with cholangiocellular carcinoma (CCC) or colorectal liver metastases. Measurements were performed using two spectrometers (Maya 2000Pro and ESA 4000), and machine-learning models, including support vector machines (SVMs) and neural networks (NNs), were trained to classify spectra as normal or tumorous. Spectral analysis revealed consistent differences between normal and malignant liver tissue in emission lines corresponding to corresponding to Mg (279.6-285.2 nm), Na (330.2 nm), Ca (393.4 and 396.9 nm), and Zn (213.5 nm). Using these data, NNs outperformed SVMs across all subgroups, increasing accuracy from 76.9% to 87.8% for metastases and from 76.0% to 88.4% for CCC. Classification performance was consistent between participating cancer centers and unaffected by sample type (fresh vs. cryopreserved). Prediction accuracy remained independent of tumor cell proportion, suggesting that NNs captured information from both tumor cells and the surrounding microenvironment. OES enables rapid, accurate, and reproducible ex vivo differentiation between normal and malignant liver tissue. With further refinement and clinical validation, this approach could complement or, in selected cases, replace intraoperative frozen sections, particularly in time-critical or resource-limited surgical settings.

Lung neuroendocrine tumours (lung NETs) are rare neoplasms comprising approximately 2% of lung cancers. Recent studies have identified distinct molecular groups based on transcriptome and methylome data, but genomic and morphological features remain underexplored due to limited whole-genome and imaging data. We have generated the largest multi-omic dataset of lung NETs to date (201 participants, for a total of n = 294 tumours), including RNA sequencing, EPIC 850K methylation arrays, and whole-genome sequencing. This multiomic dataset also include multi-regional whole-genome sequencing for 41 participants, allowing for the quantification of intra-tumoural heterogeneity. We additionally generated spatial proteomics (64 participants), spatial transcriptomics (4 participants) and whole-slide histopathology images for 212 cases. This dataset enables a comprehensive characterization of lung NET molecular groups and the identification of group-specific morphological features using deep learning algorithms. All quality control analyses, processed data, and scripts are provided to ensure reproducibility. This dataset is available as a basis for further molecular and morphological analysis of lung NETs, and for future research on multi-scale integration.

PURPOSE:CD276 (B7-H3) is an immunoregulatory protein that plays an important role in the inhibition of T-cell function. CD276 is overexpressed on a variety of human solid cancer cells with limited expression in normal tissues, making it an appealing target for innovative cancer immunotherapy approaches. Pleural mesothelioma (PM) is a highly aggressive disease with a need for new treatment options. Our objective was to investigate the expression of CD276 in the multicenter PM cohort of the European Thoracic Oncology Platform Mesoscape project and correlate the results with annotated clinical data. MATERIALS AND METHODS:Using tissue microarrays (TMAs), the expression of CD276, assessed using a semiquantitative aggregate H-score method on the membrane (and secondarily in the cytoplasm), was correlated with clinicopathologic characteristics and survival outcome. RESULTS:CD276 immunohistochemistry results were available for 353 patients, with mostly epithelioid histology (71%). Membranous CD276 expression was present in 86%. High membranous CD276 expression (H-score ≥the median H-score of 120) was significantly more common in females (P = .0029; 71% v 47%) and in epithelioid histology (P < .001; 59% v 29%), whereas no significant association in clinical outcome (overall survival [OS]/progression-free survival) was found. Cross-validation of the TMA method using whole sections revealed a moderate agreement for membranous assessment (Cohen's kappa = 0.47) and a lower agreement for cytoplasm assessment (Cohen's kappa = 0.37). In an exploratory analysis, high cytoplasmic CD276 expression was associated with worse prognosis (OS, log-rank P = .043), but was not significant when adjusting for other clinical variables. CONCLUSION:Although no prognostic value of CD276 expression was found, its high membranous expression (86%) in the PM samples of the study supports further research of its potential as a therapeutic target for this disease.

Neuroendocrine tumors (NET) of the lung constitute a rare entity of primary lung malignancies that often exhibit an indolent clinical course. Epigenetics-related differences have been described previously for lung NET, but the clinical significance remains unclear. In this study, we performed genome-wide methylation analysis using the Infinium MethylationEPIC BeadChip technology on FFPE tissues from lung NET treated at two academic centers. We aimed to investigate the methylation profiles of known prognostic subgroups. In total, 54 tissue samples from primary lung NET were analyzed, of which 37 were typical carcinoids (TC) and 17 atypical carcinoids (AC). Overall, 25/53 patients (47.2%) developed metastases throughout the disease course, 14/26 (53.8%) had a positive somatostatin receptor (SSTR) scan, and 7/28 patients (25.0%) had documented endocrine activity. Analysis of the DNA methylation data showed substantial differences between TC and AC samples and revealed three distinct clusters (C1–C3): C3 ( n = 29) with 100% TC and 89.7% non-metastasized, C2 ( n = 22) with 63.6% AC and 95.5% metastasized, and C1 with three AC samples (2/3 metastasized). In subgroup analyses, distinct methylation patterns were observed based on histology, metastases, SSTR status, and endocrine activity. In the functional gene classification, the genes affected by differential methylation were mainly involved in cell signaling. DNA methylation could potentially aid in the diagnostic process of lung NET. The differences in methylation observed with respect to clinical features like SSTR expression and endocrine activity could translate into improved management of lung NET.

The adaptive immune system plays a critical role in the anti-tumor response. Understanding the crosstalk between these immune cell subsets could uncover novel therapeutic opportunities in non-small cell lung cancer (NSCLC). Single-cell RNA sequencing (scRNA-seq) and immune repertoire sequencing were applied to CD4+ T cells, CD8+ T cells, and B cells isolated from tumor and matched normal tissues of three NSCLC patients. Findings were validated using publicly available datasets. Naïve CD4+ T cells were the predominant cell type across samples, while effector memory and cycling T cells exhibited the most significant clonal expansion. Clonally expanded T and B cell populations were detected in tumor samples from all patients. Antibody-secreting cells showed the highest clonal overlap with atypical memory B cells, suggesting an extrafollicular differentiation pathway. Ligand-receptor analysis identified the CCL5-CCR1 signaling axis as a potential interaction pathway between atypical memory B cells and clonally expanded effector memory T cells. The integration of scRNA-seq and immune repertoire analysis provides a powerful tool to study the adaptive immune response in NSCLC. The CCL5-CCR1 axis may represent a novel mechanism linking T and B cell interactions in the tumor microenvironment, warranting further exploration for therapeutic targeting. Supported by the Austrian Research Promotion Agency (FFG). Tumor Immunology: Cellular Responses and Tumor Microevironment (TIME)

Reactive oxygen species can oxidatively modify enzymes to reroute metabolism according to tumor needs, rendering identification of oxidized proteins important for understanding neoplastic survival mechanisms. Thiol groups are most susceptible to oxidative modifications but challenging to analyze in clinical settings. We here describe the protein and small-molecular thiol oxidation landscape of 70 human lung tumors (and their paired healthy counter parts) and demonstrate that cancer adapts metabolism to increase glutathione synthesis to counteract oxidative stress. Glyoxalases, the key enzymes in the detoxification of methylglyoxal, a byproduct of glycolysis and precursor of advanced glycation end-products, are compromised by oxidation and downregulation. Despite decreased methylglyoxal detoxification capacity, cancers do not accumulate advanced glycation end-products. Since in vitro downregulation or inhibition of GAPDH upregulates glyoxalases, we propose that tumors reduce methylglyoxal by activating GAPDH.

The natural history of late-onset pulmonary arterial hypertension (PAH) with features of venous/capillary involvement and the associations with rare variants in PAH genes are not well known. We report a case of a female patient who developed severe PAH at the age of 70. Two years before, lung histology was obtained showing features of pulmonary veno-occlusive disease. Genetic testing revealed that the patient was harbouring two rare genetic variants in the KDR and EIF2AK4 genes. She received a triple combination therapy alongside diuretics and survived remarkable 8 years after the PAH diagnosis.

The 2021 WHO classification of thoracic tumours recommends grading pleural mesothelioma to aid prognostication. Robustness of grading and morphological characterisation is key to its clinical utility, though validation of this grading system has largely been conducted by expert thoracic pathologists. We conducted a survey inviting pathologists across a range of practices and expertise to grade digitised images of 50 epithelioid pleural mesotheliomas that had been graded by an expert in thoracic pathology. We included slides that were considered potentially problematic such as small biopsies, focal necrosis, and rare subtypes that may affect grading (small cell and deciduoid features). Using the Sectra Uniview web viewer, participants were asked to score atypia, mitotic count, and necrosis and choose from a list of cytological and architectural features. Seventy-four pathologists anonymously participated. There was 90% agreement of consensus scores with expert opinion using the WHO 2-tier grade and 72% for the 3-tier nuclear grade but only 70% for nuclear atypia, 56% for mitoses, and 84% for necrosis. Both 3-tier nuclear grade and WHO 2-tier grading systems were significantly associated with survival. Our study affirms the overall robustness and utility of grading for pleural mesothelioma, reveals variances, and suggests the need for dedicated training.