Poor Applicability of Currently Available Prognostic Scoring Systems for Prediction of Outcome in KIT D816V-Negative Advanced Systemic Mastocytosis.

Within our nationwide registry, we identified a KIT D816V mutation (KIT D816Vpos.) in 280/299 (94%) patients with advanced systemic mastocytosis (AdvSM). Age, cytopenias and the presence of additional somatic mutations confer inferior overall survival (OS). However, little is known about the characteristics of KIT D816V-negative (D816Vneg.) AdvSM. In 19 D816Vneg. patients, a combination of clinical, morphological and genetic features revealed three subgroups: (a) KIT D816H- or Y-positive SM (KIT D816H/Ypos., n = 7), predominantly presenting as mast cell leukemia (MCL; 6/7 patients), (b) MCL with negative KIT sequencing (KITneg. MCL, n = 7) and (c) KITneg. SM with associated hematologic neoplasm (KITneg. SM-AHN, n = 5). Although >70% of patients in the two MCL cohorts (KIT D816H/Ypos. and KITneg.) were classified as low/intermediate risk according to prognostic scoring systems (PSS), treatment response was poor and median OS was shorter than in a KIT D816Vpos. MCL control cohort (n = 29; 1.7 vs. 0.9 vs. 2.6 years; p < 0.04). The KITneg. SM-AHN phenotype was dominated by the heterogeneous AHN (low mast cell burden, presence of additional mutations) with a better median OS of 4.5 years. We conclude that (i) in MCL, negativity for D816V is a relevant prognostic factor and (ii) PSS fail to correctly classify D816Vneg. patients.

Generation of complex bone marrow organoids from human induced pluripotent stem cells.

The human bone marrow (BM) niche sustains hematopoiesis throughout life. We present a method for generating complex BM-like organoids (BMOs) from human induced pluripotent stem cells (iPSCs). BMOs consist of key cell types that self-organize into spatially defined three-dimensional structures mimicking cellular, structural and molecular characteristics of the hematopoietic microenvironment. Functional properties of BMOs include the presence of an in vivo-like vascular network, the presence of multipotent mesenchymal stem/progenitor cells, the support of neutrophil differentiation and responsiveness to inflammatory stimuli. Single-cell RNA sequencing revealed a heterocellular composition including the presence of a hematopoietic stem/progenitor (HSPC) cluster expressing genes of fetal HSCs. BMO-derived HSPCs also exhibited lymphoid potential and a subset demonstrated transient engraftment potential upon xenotransplantation in mice. We show that the BMOs could enable the modeling of hematopoietic developmental aspects and inborn errors of hematopoiesis, as shown for human VPS45 deficiency. Thus, iPSC-derived BMOs serve as a physiologically relevant in vitro model of the human BM microenvironment to study hematopoietic development and BM diseases.

Genetics and beyond: Precision Medicine Real-World Data for Patients with Cervical, Vaginal or Vulvar Cancer in a Tertiary Cancer Center.

Advances in molecular tumor diagnostics have transformed cancer care. However, it remains unclear whether precision oncology has the same impact and transformative nature across all malignancies. We conducted a retrospective analysis of patients with human papillomavirus (HPV)-related gynecologic malignancies who underwent comprehensive molecular profiling and subsequent discussion at the interdisciplinary Molecular Tumor Board (MTB) of the University Hospital, LMU Munich, between 11/2017 and 06/2022. We identified a total cohort of 31 patients diagnosed with cervical (CC), vaginal or vulvar cancer. Twenty-two patients (fraction: 0.71) harbored at least one mutation. Fifteen patients (0.48) had an actionable mutation and fourteen (0.45) received a recommendation for a targeted treatment within the MTB. One CC patient received a biomarker-guided treatment recommended by the MTB and achieved stable disease on the mTOR inhibitor temsirolimus for eight months. Factors leading to non-adherence to MTB recommendations in other patient cases included informed patient refusal, rapid deterioration, stable disease, or use of alternative targeted but biomarker-agnostic treatments such as antibody-drug conjugates or checkpoint inhibitors. Despite a remarkable rate of actionable mutations in HPV-related gynecologic malignancies at our institution, immediate implementation of biomarker-guided targeted treatment recommendations remained low, and access to targeted treatment options after MTB discussion remained a major challenge.

A clinical, morphological and molecular study of 70 patients with gastrointestinal involvement in systemic mastocytosis.

In 70 patients with KIT D816V positive systemic mastocytosis (SM) including 36 patients with advanced SM (AdvSM), we correlated the extent of reported mucosal mast cell ([m]MC) infiltration of the upper and/or lower gastrointestinal tract (UGIT, n = 63; LGIT, n = 64; both, n = 57) with symptoms and markers of MC burden/subtype. GI symptoms were reported by all patients (mean 2.1 number of symptoms). A strong mMC infiltration was identified in 24 patients (UGIT, 17/63, 27%; LGIT, 19/64, 30%). Concurrent involvement of UGIT and LGIT (n = 12) correlated with female gender (75%) and a higher symptom burden (mean 2.7) but not with MC burden or subtype. Significant differences between non-AdvSM and AdvSM were reported regarding food intolerance (54% vs. 17%), cramping (54% vs. 22%) and weight loss (0% vs. 64%). KIT D816V was identified in 54/56 (96%) available biopsies. In 46 patients, digital PCR revealed a correlation with low albumin levels (r = - 0.270, P = 0.069) and the KIT D816V VAF in peripheral blood (r = 0.317, P = 0.036) but not with the extent of mMC infiltration or markers of MC burden/subtype. Although MC mediator triggered GI symptoms have a substantial impact on the quality of life, correlation to objective disease parameters is lacking thus making its systematic assessment challenging.

A newly identified 45-kDa JAK2 variant with an altered kinase domain structure represents a novel mode of JAK2 kinase inhibitor resistance.

Tyrosine-protein kinase (janus kinase; JAK)-signal transducer and activator of transcription (STAT) signaling plays a pivotal role in the development of myeloproliferative neoplasms (MPNs). Treatment with the potent JAK1/JAK2-specific inhibitor, ruxolitinib, significantly reduces tumor burden; however, ruxolitinib treatment does not fully eradicate the malignant clone. As the molecular basis for the disease persistence is not well understood, we set out to gain new insights by generating ruxolitinib-resistant cell lines. Surprisingly, these cells harbor a 45 kDa JAK2 variant (FERM-JAK2) consisting of the N-terminal FERM domain directly fused to the C-terminal kinase domain in 80% of sublines resistant to ruxolitinib. At the molecular level, FERM-JAK2 is able to directly bind and activate STAT5 in the absence of cytokine receptors. Furthermore, phosphorylation of activation-loop tyrosines is dispensable for FERM-JAK2-mediated STAT5 activation and cellular transformation, in contrast to JAK2-V617F. As a result, FERM-JAK2 is highly resistant to several ATP-competitive JAK2 inhibitors, whereas it is particularly sensitive to HSP90 inhibition. A murine model of FERM-JAK2 leukemogenesis showed an accelerated MPN phenotype with pronounced splenomegaly. Notably, most current protocols for the monitoring of emerging JAK variants are unable to detect FERM-JAK2, highlighting the urgent need for implementing next-generation sequencing approaches in MPN patients receiving ruxolitinib.

Development of MDS in Pediatric Patients with GATA2 Deficiency: Increased Histone Trimethylation and Deregulated Apoptosis as Potential Drivers of Transformation.

GATA2 deficiency is a heterogeneous, multisystem disorder associated with a high risk of developing myelodysplastic syndrome (MDS) and the progression to acute myeloid leukemia. The mechanisms underlying malignant transformation in GATA2 deficiency remain poorly understood, necessitating predictive markers to assess an individual's risk of progression and guide therapeutic decisions. In this study, we performed a systematic analysis of bone marrow biopsies from 57 pediatric MDS patients. Focusing on hematopoiesis and the hematopoietic niche, including its microenvironment, we used multiplex immunofluorescence combined with multispectral imaging, gene expression profiling, and multiplex RNA in situ hybridization. Patients with a GATA2 deficiency exhibited a dysregulated GATA2 transcriptional network. Disease progression (GATA2-EB, n = 6) was associated with increased GATA2 mRNA levels, restored expression of the GATA2 target EZH2, and increased H3K27me3. GATA2-EB was further characterized by the high expression of the anti-apoptotic protein BCL2, a feature absent in children with a GATA2 deficiency and refractory cytopenia of childhood (GATA2-RCC, n = 24) or other pediatric MDS subgroups (RCC, n = 17; MDS-EB, n = 10). The multispectral imaging analysis of additional BCL2 family members revealed significantly elevated Mediators of Apoptosis Combinatorial (MAC) scores in GATA2-EB patients. Taken together, our findings highlight the potential drivers of disease progression in GATA2 deficiency, particularly increased histone trimethylation and dysregulated apoptosis. Furthermore, upregulated BCL2 and EZH2 and increased MAC scores provide a strong rationale for the use of venetoclax and azacitidine in therapeutic regimens for GATA2-EB.

ACE2-independent SARS-CoV-2 virus entry through cell surface GRP78 on monocytes - evidence from a translational clinical and experimental approach.

BACKGROUND: SARS-CoV-2 infects host cells via an ACE2/TMPRSS2 entry mechanism. Monocytes and macrophages, which play a key role during severe COVID-19 express only low or no ACE2, suggesting alternative entry mechanisms in these cells. In silico analyses predicted GRP78, which is constitutively expressed on monocytes and macrophages, to be a potential candidate receptor for SARS-CoV-2 virus entry. METHODS: Hospitalized COVID-19 patients were characterized regarding their pro-inflammatory state and cell surface GRP78 (csGRP78) expression in comparison to healthy controls. RNA from CD14+ monocytes of patients and controls were subjected to transcriptome analysis that was specifically complemented by bioinformatic re-analyses of bronchoalveolar lavage fluid (BALF) datasets of COVID-19 patients with a focus on monocyte/macrophage subsets, SARS-CoV-2 infection state as well as GRP78 gene expression. Monocyte and macrophage immunohistocytochemistry on GRP78 was conducted in post-mortem lung tissues. SARS-CoV-2 spike and GRP78 protein interaction was analyzed by surface plasmon resonance, GST Pull-down and Co-Immunoprecipitation. SARS-CoV-2 pseudovirus or single spike protein uptake was quantified in csGRP78high THP-1 cells. FINDINGS: Cytokine patterns, monocyte activation markers and transcriptomic changes indicated typical COVID-19 associated inflammation accompanied by upregulated csGRP78 expression on peripheral blood and lung monocytes/macrophages. Subsequent cell culture experiments confirmed an association between elevated pro-inflammatory cytokine levels and upregulation of csGRP78. Interaction of csGRP78 and SARS-CoV-2 spike protein with a dissociation constant of KD = 55.2 nM was validated in vitro. Infection rate analyses in ACE2low and GRP78high THP-1 cells showed increased uptake of pseudovirus expressing SARS-CoV-2 spike protein. INTERPRETATION: Our results demonstrate that csGRP78 acts as a receptor for SARS-CoV-2 spike protein to mediate ACE2-independent virus entry into monocytes. FUNDING: Funded by the Sino-German-Center for Science Promotion (C-0040) and the Germany Ministry BMWi/K [DLR-grant 50WB1931 and RP1920 to AC, DM, TW].

A Retrospective Analysis of Biliary Tract Cancer Patients Presented to the Molecular Tumor Board at the Comprehensive Cancer Center Munich.

BACKGROUND AND OBJECTIVE: With the rising importance of precision oncology in biliary tract cancer (BTC), the aim of this retrospective single-center analysis was to describe the clinical and molecular characteristics of patients with BTC who underwent comprehensive genomic profiling (CGP) and were discussed in the CCCMunichLMU molecular tumor board (MTB). PATIENTS AND METHODS: In this single-center observational study, we included BTC patients with intrahepatic cholangiocarcinoma (iCCA), extrahepatic CCA (eCCA), and gallbladder cancer (GB), who had been discussed in the institutional MTB from May 29, 2017, to July 25, 2022. Patients were followed up until 31 January 2023. Data were retrospectively collected by review of medical charts, and MTB recommendation. RESULTS: In total, 153 cases were registered to the MTB with a median follow-up of 15 months. Testing was successful in 81.7% of the patients. CGP detected targetable alterations in 35.3% of our BTC patients (most commonly ARID1A/ERBB2/IDH1/PIK3CA/BRAF-mutations and FGFR2-fusions). Recommendations for molecularly guided therapy were given in 46.4%. Of those, treatment implementation of targeted therapy followed in 19.4%. In patients receiving the recommended treatment, response rate was 57% and median overall survival was 19 months (vs 8 months in the untreated cohort). The progression-free survival ratio of 1.45 suggest a clinical benefit of molecularly guided treatment. CONCLUSIONS: In line with previous work, our series demonstrates feasibility and clinical utility of comprehensive genomic profiling in BTC patients. With the growing number of targeted agents with clinical activity in BTC, CGP should become standard of care in the management of this group of patients.

The Absolute Monocyte Count at Diagnosis Affects Prognosis in Myelodysplastic Syndromes Independently of the IPSS-R Risk Score.

The absolute monocyte count (AMC) is associated with mortality in a variety of medical conditions. Its prognostic impact in myelodysplastic syndromes (MDSs) is less well studied. Therefore, we investigated its potential prognostic value in a cohort from the Düsseldorf MDS registry in relationship to the revised international prognostic scoring system (IPSS-R). An AMC below the population's median (<0.2 × 109/L) was associated with several adverse disease features such as lower haemoglobin levels, lower count of neutrophils and platelets, and a higher percentage of blasts in the bone marrow. MDS patients with an AMC < 0.2 × 109/L had a significantly higher risk of progression into acute myeloid leukemia (AML). In a univariate, proportional hazards model the effect of the AMC as a continuous variable was modelled via p-splines. We found a U-shaped effect with the lowest hazard around 0.3 × 109/L. Accordingly, an AMC within the last quartile of the population (0.4 × 109/L) was associated with a reduced overall survival independently of IPSS-R, but not with the risk of secondary AML. Considering monocytopenia as a risk factor for AML progression in MDS may provide an additional argument for allogeneic transplantation or the use of hypomethylating agents in patients who are not clear candidates for those treatments according to current prognostic scoring systems and/or recommendations. Further studies are needed to assess the prognostic impact of the AMC in the context of prognostic scoring systems, considering the molecular risk profile, and to identify the mechanisms responsible for the higher mortality in MDS patients with a subtle monocytosis.

Post-therapeutic microRNA-146a in liquid biopsies may determine prognosis in metastatic gastrointestinal cancer patients receiving 90Y-radioembolization.

PURPOSE: The role of microRNA-146a (miR-146a) in defining the tumor immune microenvironment (TIME) is well established. The aim of this study was to evaluate circulating miR-146a as an early prognostic marker of 90Y-radioembolization (90Y-RE) in metastatic liver cancer and to assess the correlation between circulating miR-146a and TIME cellular composition in distant, yet untreated metastases. METHODS: Twenty-one patients with bilobar liver lesions from gastro-intestinal cancer underwent lobar 90Y-RE. Biopsy of contralateral lobe abscopal tumors was acquired at the onset of a second treatment session at a median of 21 days after initial RE, immediately prior to ablation therapy of the contralateral lobe tumor. miR-146a was measured by RT-qPCR in plasma collected 24 h before (T1) and 48 h after (T2) initial unilobar 90Y-RE. The level of miR-146a was correlated with the infiltration of CD4 + , CD8 + , FoxP3 T cells, CD163 + M2 macrophages and immune-exhausted T cells in the abscopal tumor tissue acquired before the second treatment session. RESULTS: Plasma samples collected at T2 showed a higher concentration of miR-146a with respect to T1 in 43% of the patients (p = 0.002). In these patients, tumors revealed a pro-tumorigenic immune composition with enrichment of Tim3 + immune exhausted cells (p = 0.021), in combination with a higher infiltration of CD163 + M2 macrophages and a lower infiltration of CD8 + T cells. Patients with a higher level of miR-146a after 90Y-RE showed a trend to shorter OS (p = 0.055). CONCLUSION: miR-146a may represent a novel prognostic biomarker for 90Y-radioembolization in metastatic liver cancer.

P2X1 and P2X7 Receptor Overexpression Is a Negative Predictor of Survival in Muscle-Invasive Bladder Cancer.

Bladder cancer is amongst the most common causes of cancer death worldwide. Muscle-invasive bladder cancer (MIBC) bears a particularly poor prognosis. Overexpression of purinergic P2X receptors (P2XRs) has been associated with worse outcome in several malignant tumors. Here, we investigated the role of P2XRs in bladder cancer cell proliferation in vitro and the prognostic value of P2XR expression in MIBC patients. Cell culture experiments with T24, RT4, and non-transformed TRT-HU-1 cells revealed a link between high ATP concentrations in the cell culture supernatants of bladder cell lines and a higher grade of malignancy. Furthermore, proliferation of highly malignant T24 bladder cancer cells depended on autocrine signaling through P2X receptors. P2X1R, P2X4R, and P2X7R expression was immunohistochemically analyzed in tumor specimens from 173 patients with MIBC. High P2X1R expression was associated with pathological parameters of disease progression and reduced survival time. High combined expression of P2X1R and P2X7R increased the risk of distant metastasis and was an independent negative predictor of overall and tumor-specific survival in multivariate analyses. Our results suggest that P2X1R/P2X7R expression scores are powerful negative prognostic markers in MIBC patients and that P2XR-mediated pathways are potential targets for novel therapeutic strategies in bladder cancer.

The International Consensus Classification (ICC) of hematologic neoplasms with germline predisposition, pediatric myelodysplastic syndrome, and juvenile myelomonocytic leukemia.

Updating the classification of hematologic neoplasia with germline predisposition, pediatric myelodysplastic syndrome (MDS), and juvenile myelomonocytic leukemia (JMML) is critical for diagnosis, therapy, research, and clinical trials. Advances in next-generation sequencing technology have led to the identification of an expanding group of genes that predispose to the development of hematolymphoid neoplasia when mutated in germline configuration and inherited. This review encompasses recent advances in the classification of myeloid and lymphoblastic neoplasia with germline predisposition summarizing important genetic and phenotypic information, relevant laboratory testing, and pathologic bone marrow features. Genes are organized into three major categories including (1) those that are not associated with constitutional disorder and include CEBPA, DDX41, and TP53; (2) those associated with thrombocytopenia or platelet dysfunction including RUNX1, ANKRD26, and ETV6; and (3) those associated with constitutional disorders affecting multiple organ systems including GATA2, SAMD9, and SAMD9L, inherited genetic mutations associated with classic bone marrow failure syndromes and JMML, and Down syndrome. A provisional category of germline predisposition genes is created to recognize genes with growing evidence that may be formally included in future revised classifications as substantial supporting data emerges. We also detail advances in the classification of pediatric myelodysplastic syndrome (MDS), expanding the definition of refractory cytopenia of childhood (RCC) to include early manifestation of MDS in patients with germline predisposition. Finally, updates in the classification of juvenile myelomonocytic leukemia are presented which genetically define JMML as a myeloproliferative/myelodysplastic disease harboring canonical RAS pathway mutations. Diseases with features overlapping with JMML that do not carry RAS pathway mutations are classified as JMML-like. The review is based on the International Consensus Classification (ICC) of Myeloid and Lymphoid Neoplasms as reported by Arber et al. (Blood 140(11):1200-1228, 2022).

The OTUD6B-LIN28B-MYC axis determines the proliferative state in multiple myeloma.

Deubiquitylases (DUBs) are therapeutically amenable components of the ubiquitin machinery that stabilize substrate proteins. Their inhibition can destabilize oncoproteins that may otherwise be undruggable. Here, we screened for DUB vulnerabilities in multiple myeloma, an incurable malignancy with dependency on the ubiquitin proteasome system and identified OTUD6B as an oncogene that drives the G1/S-transition. LIN28B, a suppressor of microRNA biogenesis, is specified as a bona fide cell cycle-specific substrate of OTUD6B. Stabilization of LIN28B drives MYC expression at G1/S, which in turn allows for rapid S-phase entry. Silencing OTUD6B or LIN28B inhibits multiple myeloma outgrowth in vivo and high OTUD6B expression evolves in patients that progress to symptomatic multiple myeloma and results in an adverse outcome of the disease. Thus, we link proteolytic ubiquitylation with post-transcriptional regulation and nominate OTUD6B as a potential mediator of the MGUS-multiple myeloma transition, a central regulator of MYC, and an actionable vulnerability in multiple myeloma and other tumors with an activated OTUD6B-LIN28B axis.

PARP14 is a novel target in STAT6 mutant follicular lymphoma.

The variable clinical course of follicular lymphoma (FL) is determined by the molecular heterogeneity of tumor cells and complex interactions within the tumor microenvironment (TME). IL-4 producing follicular helper T cells (TFH) are critical components of the FL TME. Binding of IL-4 to IL-4R on FL cells activates JAK/STAT signaling. We identified STAT6 mutations (STAT6MUT) in 13% of FL (N = 33/258), all clustered within the DNA binding domain. Gene expression data and immunohistochemistry showed upregulation of IL-4/STAT6 target genes in STAT6MUT FL, including CCL17, CCL22, and FCER2 (CD23). Functionally, STAT6MUT was gain-of-function by serial replating phenotype in pre-B CFU assays. Expression of STAT6MUT enhanced IL-4 induced FCER2/CD23, CCL17 and CCL22 expression and was associated with nuclear accumulation of pSTAT6. RNA sequencing identified PARP14 -a transcriptional switch and co-activator of STAT6- among the top differentially upregulated genes in IL-4 stimulated STAT6MUT lymphoma cells and in STAT6MUT primary FL cells. Quantitative chromatin immunoprecipitation (qChIP) demonstrated binding of STAT6MUT but not STAT6WT to the PARP14 promotor. Reporter assays showed increased IL-4 induced transactivation activity of STAT6MUT at the PARP14 promotor, suggesting a self-reinforcing regulatory circuit. Knock-down of PARP14 or PARP-inhibition abrogated the STAT6MUT gain-of-function phenotype. Thus, our results identify PARP14 as a novel therapeutic target in STAT6MUT FL.

Suppression of SARS-CoV-2 Replication with Stabilized and Click-Chemistry Modified siRNAs.

The emergence of more transmissible or aggressive variants of SARS-CoV-2 requires the development of antiviral medication that is quickly adjustable to evolving viral escape mutations. Here we report the synthesis of chemically stabilized small interfering RNA (siRNA) against SARS-CoV-2. The siRNA can be further modified with receptor ligands such as peptides using CuI -catalysed click-chemistry. We demonstrate that optimized siRNAs can reduce viral loads and virus-induced cytotoxicity by up to five orders of magnitude in cell lines challenged with SARS-CoV-2. Furthermore, we show that an ACE2-binding peptide-conjugated siRNA is able to reduce virus replication and virus-induced apoptosis in 3D mucociliary lung microtissues. The adjustment of the siRNA sequence allows a rapid adaptation of their antiviral activity against different variants of concern. The ability to conjugate the siRNA via click-chemistry to receptor ligands facilitates the construction of targeted siRNAs for a flexible antiviral defence strategy.

International Consensus Classification of Myeloid Neoplasms and Acute Leukemias: integrating morphologic, clinical, and genomic data.

The classification of myeloid neoplasms and acute leukemias was last updated in 2016 within a collaboration between the World Health Organization (WHO), the Society for Hematopathology, and the European Association for Haematopathology. This collaboration was primarily based on input from a clinical advisory committees (CACs) composed of pathologists, hematologists, oncologists, geneticists, and bioinformaticians from around the world. The recent advances in our understanding of the biology of hematologic malignancies, the experience with the use of the 2016 WHO classification in clinical practice, and the results of clinical trials have indicated the need for further revising and updating the classification. As a continuation of this CAC-based process, the authors, a group with expertise in the clinical, pathologic, and genetic aspects of these disorders, developed the International Consensus Classification (ICC) of myeloid neoplasms and acute leukemias. Using a multiparameter approach, the main objective of the consensus process was the definition of real disease entities, including the introduction of new entities and refined criteria for existing diagnostic categories, based on accumulated data. The ICC is aimed at facilitating diagnosis and prognostication of these neoplasms, improving treatment of affected patients, and allowing the design of innovative clinical trials.

Checkpoint-inhibitor induced Polyserositis with Edema.

BACKGROUND: As immune checkpoint inhibitors (ICI) are increasingly being used due to effectiveness in various tumor entities, rare side effects occur more frequently. Pericardial effusion has been reported in patients with advanced non-small cell lung cancer (NSCLC) after or under treatment with immune checkpoint inhibitors. However, knowledge about serositis and edemas induced by checkpoint inhibitors in other tumor entities is scarce. METHODS AND RESULTS: Four cases with sudden onset of checkpoint inhibitor induced serositis (irSerositis) are presented including one patient with metastatic cervical cancer, two with metastatic melanoma and one with non-small cell lung cancer (NSCLC). In all cases treatment with steroids was successful in the beginning, but did not lead to complete recovery of the patients. All patients required multiple punctures. Three of the patients presented with additional peripheral edema; in one patient only the lower extremities were affected, whereas the entire body, even face and eyelids were involved in the other patients. In all patients serositis was accompanied by other immune-related adverse events (irAEs). CONCLUSION: ICI-induced serositis and effusions are complex to diagnose and treat and might be underdiagnosed. For differentiation from malignant serositis pathology of the punctured fluid can be helpful (lymphocytes vs. malignant cells). Identifying irSerositis as early as possible is essential since steroids can improve symptoms.