Diffuse midline H3K27-altered glioma in an atypical location mimicking a medulloblastoma.

Background: Diffuse midline glioma (DMG) with H3 histones in lysine 27 (H3K27) mutation is an aggressive central nervous system tumor that primarily affects children. It often presents with nonspecific neurological symptoms and can mimic other posterior fossa tumors, such as medulloblastoma, on imaging. Due to its poor prognosis and rapid progression, early recognition and accurate diagnosis are crucial for patient management. Case Description: We present the case of a 10-year-old girl who developed progressively worsening neurological symptoms, raising suspicion of a posterior fossa tumor. Initial magnetic resonance imaging findings suggested a diagnosis of medulloblastoma. However, after surgical resection, pathological analysis confirmed the presence of a DMG with an H3K27 mutation. Despite the successful resection of a substantial portion of the tumor, the disease progressed rapidly, with tumor dissemination occurring within six months of diagnosis. Conclusion: This case highlights the importance of considering DMG, particularly with H3K27 alterations, as a differential diagnosis in posterior fossa tumors. The presence of these genetic mutations significantly impacts both treatment decisions and prognosis. The variability in clinical presentation and tumor morphology associated with DMG underscores the need for thorough evaluation to optimize treatment strategies and further our understanding of this complex entity.