CD90 expression in atypical meningiomas and meningioma metastasis.

OBJECTIVES Meningiomas are slow-growing intracranial/intraspinal tumors, with a wide range of histopathologic variants. The more aggressive atypical and malignant types can disseminate via the venous system, lymphatic, system, or cerebrospinal fluid, with the lung and pleura being the most common sites of extracranial metastases. A case of metastatic meningioma with high expression of CD90 was spotted during a review of flow cytometry data for lung malignancies. Therefore, we have analyzed CD90 expression in a series of meningioma metastases with their corresponding primary tumors and in a series of 92 primary meningioma tumors. METHODS In addition to flow cytometry and immunohistochemical analysis of the case, a series of meningiomas and relative metastases has been evaluated for CD90 immunohistochemical expression. Furthermore, an immunohistochemical analysis has been conducted in a tissue microarray, including typical and atypical meningiomas. RESULTS CD90 had high expression in three of four cases of metastases and in their corresponding primary atypical meningioma. In addition, CD90 was significantly expressed in atypical rather than in typical meningiomas (P = .003). However, the correlation of CD90 with patient survival reveals only a trend of statistical association with extracranial metastases. CONCLUSIONS CD90 is a biomarker overexpressed in atypical meningioma, with a potential role in metastatic switch of this tumor.