Epithelial differentiation in intraspinal meningiomas.

To investigate the epithelial features of intraspinal meningiomas, 25 intraspinal meningiomas and 25 intracranial meningiomas were examined for the presence of pseudopsammoma bodies with hematoxylin-eosin and periodic acid-Schiff staining. In addition, we investigated the expression of keratin and epithelial membrane antigen (EMA) by immunohistochemical methods. Pseudopsammoma bodies were found in 3 of 25 cases of intracranial meningiomas (12%), but no definitive pseudopsammoma bodies were observed the intraspinal meningiomas. Three cases (12%) of intraspinal meningiomas and 9 cases (36%) of intracranial meningiomas, including 3 cases with pseudopsammoma bodies, were immunoreactive for keratin. All 25 (100%) intracranial meningiomas and 20 of 25 (84%) intraspinal meningiomas were reactive for EMA. In the intraspinal meningiomas, 4 of 25 cases (16%) showed no reactivity for EMA. These findings suggest that the origin of certain cell components of meningiomas may be different according to the site of the tumor or that the nature of meningioma may be modified by the local environment.