A 6-year-old girl with an extra-axial mass in the middle cranial fossa.

A 6-year-old Japanese girl presented with psychomotor seizures. Magnetic resonance (MR) images disclosed a mass lesion in the left middle cranial fossa with an internal irregular-shaped area, which was hyperintense on T1-weighted images and hypointense on T2-weighted images. Gross total resection of the tumor was performed through left occipital craniotomy. The tumor was white-to-grayish hard tissue, focally showing blackish pigmentation. Histological, immunohistochemical and electron-microscopical analyses revealed that white-to-grayish hard tissue corresponded to an atypical meningioma, and the blackish pigmentation of the tumor was composed of non-neoplastic, reactive hyperplasia and colonization of meningeal melanocytes in the meningioma tissue. A meningioma with reactive hyperplasia and colonization of meningeal melanocytes is unusual, but it is clinically important to differentiate this entity from other melanocytic tumors.