Subfrontal schwannoma mimicking neuroblastoma: case report

Abstract

Computed tomography (CT), performed in a healthy 28-year-old man after minor head injury, detected a frontal base tumor. Neurological examination revealed left hyposmia. On magnetic resonance imaging scans, there was a heterogeneously enhanced tumor located in the left paramedian frontal base with extension into the left ethmoid sinus. Angiography showed a hypervascular mass in the left anterior cranial fossa; it was mainly fed by the left ethmoidal artery. Positron emission tomography scanning showed moderate accumulation of 11-methylmethionine and low accumulation of 18-fluorodeoxyglucose (FDG) at the tumor site. Bone image CT disclosed compressive, nondestructive deformation of the left frontal base. The preoperative diagnosis was olfactory neuroblastoma or meningioma. The tumor was totally resected via bifrontal craniotomy. The tumor was histologically diagnosed as typical schwannoma; it was positive for S-100 protein. We report a rare subfrontal schwannoma with extension into the nasal cavity that mimicked neuroblastoma. Low FDG accumulation and compressive deformation of the anterior skull base may help in the differential diagnosis of these tumors.

Keywords: Subfrontal schwannoma; neuroblastoma; olfactory nerve; skull base.

Figure 1

(A) Axial T2-weighted magnetic resonance imaging (MRI) revealing a subfrontal heterogeneously hyperintense mass. (B) Sagittal MRI with gadolinium demonstrating an enhanced subfrontal mass with extension to the ethmoid sinus. (C) Coronal computed tomography showing erosion of the left cribriform plate.

Figure 2

Digital subtraction angiogram with left internal carotid artery injection showing the hypertrophic ophthalmic artery feeding the subfrontal mass.

Figure 3

(A) Methionine positron emission tomography (PET) imaging showing a moderate-attenuation lesion in the frontal lobe. (B) The tumor was not identified on fluorodeoxyglucose PET.

Figure 4

Postoperative magnetic resonance imaging with gadolinium demonstrating total resection of the tumor and a small hemorrhagic scar at the tumor site.

Figure 5

Histopathologic examination of the surgical specimen showed that the tumor consisted of alternating areas of compact, elongated cells (Antoni type A) and less cellularized areas (Antoni type B) (hematoxylin and eosin; A × 50, B × 100). On immunohistochemical staining, the tumor cells were positive for S-100 protein (C) (×100).