Background/Objectives: Diffuse midline glioma (DMG), H3 K27M-altered, represents a rare group of gliomas arising in midline structures of the central nervous system. Historically regarded as a pediatric entity, it is now increasingly recognized in adults. Although its relative prevalence among all midline diffuse gliomas and its clinical-radiological characteristics are well defined in children, these tumors remain less characterized in adults, and comparative evaluations with H3 K27 wildtype midline diffuse gliomas are limited. Methods: Consecutive adult patients with histopathologically confirmed diffuse glioma (WHO grade ≥ 2) diagnosed between 2016 and 2025 were retrospectively screened for midline tumor location, with systematic revision of imaging and pathology. For identified midline diffuse gliomas, comprehensive clinical, imaging, and immunohistochemical data were collected, and a detailed morphometric analysis was performed. H3 K27 alteration status was established immunohistochemically, with supplementary immunostaining when necessary. Descriptive and comparative analyses were conducted. Results: A total of 5% of the 541 adult diffuse gliomas were midline, and 23% of IDH wildtype midline gliomas were consistent with DMG, H3 K27-altered (all H3 K27M-mutant). The affected patients were significantly younger, and these tumors predominantly involved the thalamus and mesencephalon. Morphometric analyses revealed trends toward fewer high-grade features in H3 K27-altered tumors, with composite scores demonstrating significant discriminatory ability. The overall survival was not significantly different between groups but showed associations with ring-like enhancement as well as adjuvant and salvage therapies in the overall midline cohort. Conclusions: This study provides population-based prevalence estimates for DMG, H3 K27M-altered, and complements the limited literature with comparative clinical-radiological and morphometric data of potential prognostic relevance.

Solitary fibrous tumour is an uncommon, predominantly benign tumour of mesenchymal origin, developing mainly in the thoracic cavity and on the pleural surface, although it has been reported in a wide variety of extrapleural sites. Its occurrence in the liver is particularly rare. We present the case of a 57-year-old woman in whom a large mass was identified in the left lobe of the liver, demonstrating inhomogeneous contrast enhancement without significant compression of the abdominal vessels. The lesion measured 170 mm in its greatest diameter and severely destroyed the surrounding liver parenchyma. SFT is characterised by haphazardly arranged ovoid and spindle-shaped cells with numerous mildly staghorn-like vessels lined by flattened endothelium. It typically shows NAB2–STAT6 gene rearrangement with CD34 and/or STAT6 positivity on immunohistochemistry. Since imaging methods are not specific regarding the nature of the lesion, pathological and immunohistochemical analyses are essential for establishing an accurate diagnosis and assessing differential diagnostic possibilities.