Malignant Transformation of Vestibular Schwannoma at First Occurrence without Prior Irradiation.

Intracranial malignant peripheral nerve sheath tumours (MPNST) arising from the vestibulocochlear nerve are quite rare. Due to the increasing use of stereotactic radiosurgery worldwide for benign intracranial lesions, the literature available has primarily focused on the post-radiotherapy malignant transformation of vestibular schwannomas (VSs). To date, very few cases have been reported enlightening the occurrence of MPNST without prior irradiation or a history of neurofibromatosis. We report a rare case of cerebellopontine angle tumour in a 39-year female who presented with right-sided sensorineural hearing loss and facial palsy for four months without prior history of radiosurgery. The diagnosis was low-grade MPNST arising in the background of vs. based on mitosis, loss of H3K27me3, and radiologically infiltrative borders. The main objective of this case report was to emphasise the need for a cautious assessment of VSs with hypercellularity and atypia for mitosis, necrosis and invasion to exclude malignancy. Key Words: Schwannoma, malignant peripheral nerve sheath tumour, neurofibromatosis, vestibular.