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Merkel cell carcinoma (MCC) is an aggressive skin cancer frequently caused by genomic integration of the Merkel cell polyomavirus (MCPyV). MCPyV‐negative cases often present as combined MCCs, which represent a distinctive subset of tumors characterized by association of an MCC with a second tumor component, mostly squamous cell carcinoma. Up to now, only exceptional cases of combined MCC with neuroblastic differentiation have been reported. Herein we describe two additional combined MCCs with neuroblastic differentiation and provide comprehensive morphologic, immunohistochemical, transcriptomic, genetic and epigenetic characterization of these tumors, which both arose in elderly men and appeared as an isolated inguinal adenopathy. Microscopic examination revealed biphasic tumors combining a poorly differentiated high‐grade carcinoma with a poorly differentiated neuroblastic component lacking signs of proliferation. Immunohistochemical investigation revealed keratin 20 and MCPyV T antigen (TA) in the MCC parts, while neuroblastic differentiation was confirmed in the other component in both cases. A clonal relation of the two components can be deduced from 20 and 14 shared acquired point mutations detected by whole exome analysis in both combined tumors, respectively. Spatial transcriptomics demonstrated a lower expression of stem cell marker genes such as SOX2 and MCM2 in the neuroblastic component. Interestingly, although the neuroblastic part lacked TA expression, the same genomic MCPyV integration and the same large T‐truncating mutations were observed in both tumor parts. Given that neuronal transdifferentiation upon TA repression has been reported for MCC cell lines, the most likely scenario for the two combined MCC/neuroblastic tumors is that neuroblastic transdifferentiation resulted from loss of TA expression in a subset of MCC cells. Indeed, DNA methylation profiling suggests an MCC‐typical cellular origin for the combined MCC/neuroblastomas. © 2024 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland. [ABSTRACT FROM AUTHOR]

This article discusses the identification of a molecular subtype of adult-type diffuse astrocytoma with recurrent MAPK pathway alterations. Adult-type diffuse gliomas are the most common malignant primary tumors of the central nervous system, and they are classified based on the isocitrate dehydrogenase (IDH1/2) mutation status. Through DNA methylation analysis and next-generation sequencing, a distinct cluster of diffuse gliomas was identified, characterized by high-level amplification of PDGFRA and alterations in the MAPK pathway. These findings suggest potential targeted therapeutic interventions for this newly identified tumor subgroup. Further research is needed to fully understand the clinical implications of this molecular subtype. [Extracted from the article]

Amyloidosis is a rare disease especially the localized form involving pulmonary parenchyma. We report the case of a 74 years old woman who presented with chest pain and dyspnoea. CT scan showed pulmonary embolism and bilateral nodules. Laboratory examinations highlighted circulating Kappa IgM. 18F-FDG PET/CT showed intense activity of the nodules. Histological investigation supported the diagnosis of nodular pulmonary amyloidosis. There were no sign of systemic amyloidosis or autoimmune disease. No treatment was initiated: the patient remains asymptomatic after one year. Localized pulmonary amyloidosis related to MGUS was the most likely diagnosis. Malignancy, a differential diagnosis of pulmonary amyloidosis, must be excluded: histological examinations are overriding. Difference between systemic and localized amyloidosis conditions treatment and prognosis. This observation emphasizes the difficulty to establish the diagnosis of pulmonary nodular amyloidosis and the complex relationship between amyloidosis and thromboembolism.

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Background "Biopsy-only" glioblastoma (BO-GBM) is a heterogeneous, understudied group of patients associated with a poor outcome. Our objective was to explore the pattern of care and prognosis associated with BO-GBM in our center. Methods Patients with IDH wild-type BO-GBM included in a prospective regional cohort initiated in 2014 and closed in 2017 were retrospectively reviewed for patient characteristics, MRI findings, treatment allocation, and delivery. Results Of 535 patients included in the cohort, 137 patients were included in the present analysis. The median age was 66 years old and the median KPS was 70. Forty-six patients (33.6%) were referred to radiotherapy and chemotherapy (RT–TMZ) regimen, 75 (54.7%), considered unfitted for RT, received chemotherapy upfront (CT) and 16 (11.7%) were referred to palliative care (PC). Regarding the first group, 91% of patients completed the RT–TMZ. In the CT group, 11 of 75 patients (14.7%) underwent radiotherapy after chemotherapy upfront. Median overall survival was 12.3 months (95% CI, 15.30–24.16), 5.7 months (95% CI, 6.22–9.20), and 1.9 months (95% CI, 1.43–5.08) in RT–TMZ, CT, and PC groups, respectively. In multivariate analyses, progression-free survival was impacted by baseline KPS (P <.001) and MGMT status (P =.004). Overall survival was impacted by baseline KPS (P <.001) and age (P =.030). Conclusion BO-GBM constitute a large and heterogeneous population in which one-third of patients is amenable to the standard of care, with survival outcome close to one of the patients who underwent surgery. Reliable criteria are needed to help select patients for adequate treatment while new strategies are warranted for BO-GBM unfit for RT. [ABSTRACT FROM AUTHOR]

This article discusses two novel tumors classified as extraventricular neurocytomas (EVN) that were found to have NTRK2 fusions instead of the usual FGFR1 alterations. The first case involved a 23-year-old woman with migraines and epileptic seizures, while the second case involved a 15-year-old girl with intracerebral calcifications. Both cases underwent total removal of the tumors and showed positive staining for synaptophysin and olig2. The study suggests that these findings have implications for diagnosis, therapy, and terminology, and further research is needed to better understand these tumors. [Extracted from the article]

Recent epigenomic analyses have revealed the existence of a new DNA methylation class (MC) of infant‐type hemispheric glioma (IHG). Like desmoplastic infantile ganglioglioma/astrocytoma (DIG/DIA), these tumors mainly affect infants and are supratentorial. While DIG/DIA is characterized by BRAF or RAF1 alterations, IHG has been shown to have receptor tyrosine kinase (RTK) gene fusions (ALK, ROS1, NTRK1/2/3, and MET). However, in this rapidly evolving field, a more comprehensive analysis of infantile glial/glioneuronal tumors including clinical, radiological, histopathological, and molecular data is needed. Here, we retrospectively investigated data from 30 infantile glial/glioneuronal tumors, consecutively compiled from our center. They were analyzed by two experienced pediatric neuroradiologists in consensus, without former knowledge of the molecular data. We also performed a comprehensive clinical, and histopathological examination (including molecular evaluation by next‐generation sequencing, RNA sequencing, and fluorescence in situ hybridization [FISH] analyses), as well as DNA methylation profiling for the samples having sufficient material available. The integrative histopathological, genetic, and epigenetic analyses, including t‐distributed stochastic neighbor embedding (t‐SNE) analyses segregated tumors into 10 DIG/DIA (33.3%), six IHG (20.0%), three gangliogliomas (10.0%), two pleomorphic xanthoastrocytomas (6.7%), two pilocytic astrocytomas (6.7%), two supratentorial ependymomas, ZFTA fusion‐positive (6.7%), two supratentorial ependymomas, YAP1 fusion‐positive (6.7%), two embryonal tumors with PLAGL2‐family amplification (6.7%), and one diffuse low‐grade glioma, MAPK‐pathway altered. This study highlights the significant differential features, in terms of histopathology (leptomeningeal infiltration, intense desmoplasia and ganglion cells in DIG/DIA and necrosis, microvascular proliferation, and siderophages in IHG), and radiology between DIG/DIA and IHG. Moreover, these results are consistent with the literature data concerning the molecular dichotomy (BRAF/RAF1 alterations vs. RTK genes' fusions) between DIG/DIA and IHG. This study characterized histopathologically and radiologically two additional cases of the novel embryonal tumor characterized by PLAGL2 gene amplification. [ABSTRACT FROM AUTHOR]