gms | German Medical Science

Objective: Tumors involving the frontal base are most often meningiomas, carcinomas, or esthesioneuroblastomas. In this report, the authors present the rare case of a female harbouring a cellular schwannoma of the olfactory nerve.

Method: This 64-year-old woman presented with a history of 6 months permanent headache that constantly increased and finally reached an intensity of 10 on the VAS (visual analog scale). No neurological deficits were found except for a left-sided hitherto unperceived anosmia. MR imaging revealed a large, extra axial tumor of the frontal base invading into the nasal cavity. The tumor presented as partly solid, homogenously enhancing mass with further cystic areas. T2-weighted images revealed marked oedema in the surrounding brain tissue. Supposed diagnoses were meningioma or esthesioneuroblastoma, and the patient was subjected to surgery. Using a bicoronar skin incision a bifrontal approach was performed. After visualization of the tumor it instantaneously became evident that it was not a meningioma. The tumor was yellowish and of a hard structure and did not show any attachment to the dura. It was purely extra-axial and could be dissected from the surrounding brain tissue with ease. It is noteworthy that the left-sided olfactory nerve was completely destroyed by the tumor. After gross total resection of the tumor a complex frontobasal reconstruction was performed, and the postoperative course was uneventful.

Results: Histopathological examination of the resected tissue revealed a tumor with predominantly high cellular density and focal loosened texture. The cells were mainly spindle-shaped and showed focal mitotic activity. Besides strong S100 immunoreactivity, tumor cells showed a pericellular reticulin pattern and predominantly expressed CD57 but as well GFAP in a patchy fashion. Final histopathological diagnosis was cellular schwannoma WHO Grade I.

Conclusions: Even though of very rare occurrence we propose to consider not only olfactory ensheathing cell tumor but also olfactory nerve schwannoma as differential diagnosis in the event of frontal base tumor.