Adult H3K27M-mutant diffuse midline glioma with gliomatosis cerebri growth pattern: Case report and review of the literature

INTRODUCTION: H3K27M-mutant diffuse midline glioma is a recently classified unique entity predominantly affecting pediatric patients and rarely adults. The clinicopathologic features in adults remain poorly characterized. PRESENTATION OF CASE: A 36-year-old man presented with subacute progressive cognitive and visual deterioration, and hydrocephalus requiring ventricular shunting. MRI revealed a diffusely infiltrating lesion with a gliomatosis cerebri growth pattern, multiple foci of contrast enhancement, and diffuse leptomeningeal involvement. Suboccipital craniotomy with exploration of the posterior fossa revealed a subtle capsular lesion infiltrating into the choroid plexus. Although histologically low-grade, the tumor was found to have an H3K27 M mutation establishing the diagnosis. DISCUSSION: In spite of diverse clinicopathologic characteristics, H3K27M-mutant diffuse midline gliomas are incurable, WHO grade IV lesions with poor prognosis. We discuss our case in the context of a review of published reports of H3K27-mutant diffuse midline gliomas in adults. Findings late in the disease course may mimic inflammatory or infectious pathologies radiographically, and low-grade infiltrative neoplasms histologically. CONCLUSION: The diverse clinical, radiographic and molecular features of H3K27M-mutant diffuse mid line gliomas in adults remain to be completely characterized. A high index of suspicion is required to avoid missing the diagnosis. Early biopsy and detailed molecular characterization are critical for accurate diagnosis and patient counseling. (C) 2020 The Author(s). Published by Elsevier Ltd on behalf of IJS Publishing Group Ltd.