Olfactory ensheathing cell tumour: case report and literature review.

Olfactory ensheathing cell tumour (OECT) and olfactory groove schwannoma (OGS) are among the rarest intracranial tumour types that develop within anterior cranial fossa. These tumours share several similarities, including radiological and histological aspects, and only immunohistochemical staining can differentiate between them. We report a case of OECT occurring in a 28-year-old woman with a history of complex partial seizures, emotional lability and anosmia. Radiological features showed a predominantly left subfrontal extra-axial mass. Total excision of the tumour, connected to the cribriform plate and contiguous to the left olfactory bulb, was performed. Histological examination suggested an atypical schwannoma; however, immunohistochemical staining was strongly positive for S-100 protein but negative for both epithelial membrane antigen (EMA) and CD 57 (Leu-7). The final diagnosis was olfactory ensheathing cell tumour. We describe the third case of OECT and emphasize the important role of immunohistochemical staining in diagnosis: awareness of this entity, and use of immunohistochemistry help to distinguish it from OGS.