A pilocytic astrocytoma mimicking a clinoidal meningioma

Abstract

Pilocytic astrocytomas and meningiomas are benign, primary brain tumors that may involve the optic tract. Classically, the presence of a dural "tail" sign may differentiate a meningioma from other intracranial lesions. In this report, we describe a mass with the typical appearance of a clinoidal meningioma on magnetic resonance imaging (MRI) but postoperatively diagnosed as a pilocytic astrocytoma. This case illustrates the rare occurrence of a pilocytic astrocytoma mimicking a meningioma on MRI.

Figure 1

(a) Axial, (b) coronal, and (c) sagittal T1-weighted MRI showing a homogenously enhancing lesion, measuring 2.9 × 3.0 × 2.0 cm in the right clinoidal region. There is probable extension into the right optic canal, sphenoid sinus, right temporal fossa, and possibly right cavernous sinus, suggestive of a right clinoidal meningioma.

Figure 2

(a) The tumor consists of piloid cells and shows abundant mucin and Rosenthal fibers (upper left) (H&E stain; original magnification 200x). (b) A few perivascular pseudorosettes were noted, here in longitudinal section (H&E stain; original magnification 200x).