Fig. 1.

The T2-weighted (A) and postcontrast T1-weighted images (B) show a mass in the right cerebellopontine angle cistern with extension into the ipsilateral Meckel's cave. The mass shows a slightly heterogeneous lobulated contour with similar or slightly higher signal intensity than the cortex on the T2-weighted images, with heterogeneous enhancement. Edema is noted in the pons and cerebellum adjacent to the mass. Noncontrast CT shows spots of subtle high-attenuation within the mass (arrows), suggesting the possibility of calcification or hemorrhage. Also seen is a high-attenuation curvilinear area between the mass and the cerebellum (curved arrow), which was determined to be fibrosis on the pathologic examination (C). The ipsilateral internal auditory canal and petrous bone are free of tumor on both the CT and MRI (A-C). Immunohistochemistry demonstrates the MIC-2 antigen expression (D). Follow-up MRI reveals a new enhancing lesion abutting the anterior falx cerebri and left fovea ethmoidalis, and this suggests metastasis (E).