A combined neurofibroma-granular cell tumor of the middle cranial fossa

A case of a combined neurofibroma-granular cell tumor in a 52 years old gunsmith is presented. The tumor developed after an intracranial trigeminal nerve operation 25 years previously. The solid tumor in the left middle cranial fossa had displaced and infiltrated the temporal lobe. It had expanded via the optic nerve into the left orbit, and further the apex partis petrosae was destroyed. The neurofibroma part shows histological aspects of malignancy, the granular cell tumor, considering its infiltrating and destructive growth, may be regarded as malignant as well. In intermingling portions of the tumor, transitional types of fiber-like and granular cells are prominent. In the peripheral zone of the tumor apparently reactively proliferated polynuclear astrocytes are seen with occasionally intracytoplasmatic lymphocytes (emperipolesis?). A short review of the literature and the theories concerning the histogenesis of the granular cell tumor is given. Whereas most authors in recent years suggest a Schwann cell origin, based on electron microscopic findings, this intermediate tumor type motivates us to postulate a mesodermal origin of the granular cell tumor. The question of viral influence is discussed briefly.