Abstract

Posterior fossa ependymomas may be classified based on H3 p.K28Me3 (also called as H3K27Me3 or K27Me3) expression status, with group A characterized by loss of K27Me3 expression. We present a rare case of posterior fossa ependymoma with H3K27M mutation, typically associated with diffuse midline gliomas. A 5-year-old child presented with headache and vomiting. Magnetic resonance imaging (MRI) revealed a 4^th ventricular space-occupying lesion extending through the bilateral foramina of Luschka, radiologically consistent with ependymoma. Following maximal surgical resection and radiotherapy (60 Gy), the patient experienced recurrence after 1 year. Histopathological examination showed a moderately to highly cellular tumor with perivascular pseudorosettes and brisk mitotic activity. Immunohistochemistry demonstrated diffuse GFAP positivity, OLIG2 negativity, and characteristic dot-like EMA positivity. Notably, the tumor showed loss of K27Me3 expression and strong diffuse nuclear expression of H3K27M and EZH2. While H3K27M mutations are hallmark features of diffuse midline gliomas, rare cases of posterior fossa ependymomas harboring these mutations have been reported. Recent studies suggest molecular similarities between diffuse midline gliomas and posterior fossa ependymomas expressing H3K27M and EZHIP, potentially reflecting shared hindbrain developmental programs in their biological origins.

Author Details

Authors

• Sumanta Das^{1, 2}
• Bheru Dan Charan³
• Sunita Ahlawat¹
• Rakesh Kumar Gupta⁴
• Salman Shaikh⁵
• Noopur Sharma⁶
• Suman S. Karanth⁷
• Rana Patir⁵

Departments

• ¹ Department of Pathology, Agilus Diagnostics, Fortis Memorial & Research Institute, Gurugram,
• ² Department of Pathology, North Eastern Indira Gandhi Regional Institute of Health and Medical Sciences, Shillong,
• ³ Department of Radiology, All India Institute of Medical Sciences, Rishikesh,
• ⁴ Department of Radiology,
• ⁵ Department of Neurosurgery,
• ⁶ Department of Radiation Oncology, and
• ⁷ Department of Medical Oncology, Fortis Memorial & Research Institute, Gurugram, India

Address

Sumanta Das, MD
Department of Pathology
Agilus Diagnostics Ltd
Fortis Memorial Research Institute
Gurugram, India
Email: [email protected]

Citation