Intracranial neurothekeoma--a rare parenchymal nerve sheath myxoma of the middle cranial fossa.

Neurothekeomas are rare, benign nerve sheath tumors, usually arising from cutaneous nerves in the head and neck region. So far, only 4 cases of the intracranial counterpart have been reported and these were located in the posterior fossa, sellar and parasellar region. We report here the first case of neurothekeoma located deep inside the brain parenchyma. Histologically, the tumor had lobular appearance with bland morphology in spite of cellular pleomorphism, myxoid background and variable S-100 positivity, characteristics of neurothekeomas. The schwannian origin was further confirmed ultrastructurally by demonstrating basal lamina and Luse bodies. Because of its benign nature, the lesion does not need postoperative radiotherapy. Histogenesis of neurothekeoma arising in the parenchyma remains enigmatic. The probable cell of origin could be the Schwann cell or perineurial cell of the nerve twigs around the blood vessels or by extreme differentiation of the precursor cell resting in a suitable microenvironment to the schwannian phenotype.