Intracranial Hybrid Neurofibroma/Schwannoma Arising From the Olfactory Groove: A Report of an Extremely Rare Case and Review of the Literature

This is the authors' abstract. We don't add key points for this paper.

Hybrid nerve sheath tumors (HNSTs) are rare peripheral nerve sheath tumors that combine the features of schwannomas, neurofibromas, and perineuriomas. Intracranial HNSTs are extremely rare. Herein, we report the first case of an intracranial hybrid neurofibroma/schwannoma arising from the olfactory groove. A 62-year-old woman presented with right-sided hemiparesis and a gait disturbance. Magnetic resonance imaging (MRI) revealed a 45×50 mm extra-axial mass in the left anterior cranial fossa, suggestive of a meningioma or schwannoma. The patient underwent bifrontal craniotomy with complete tumor removal. Histopathological and immunohistochemical studies confirmed that the tumor consisted of two components, a neurofibroma and a schwannoma, resulting in the diagnosis of a hybrid neurofibroma/schwannoma. Whole-genome sequencing of tumor DNA revealed somatic mutations in KMT2A and trisomies of chromosomes 5 and 14q. No alterations were observed in NF1, NF2, or chromosome 22, and no germline mutations were identified. These results are not consistent with those of previously reported peripheral HNSTs, suggesting that the molecular biology of intracranial HNSTs may be different from that of peripheral HNSTs. The patient was discharged with no neurological deficits, and no recurrent findings were observed on follow-up MRI after one year. To our knowledge, this is the first reported case of an olfactory groove HNST. We highlight the importance of further studies to elucidate its pathogenesis and genetic underpinnings.