Immunohistochemical staining for claudin-1 can help distinguish meningiomas from histologic mimics.

The histologic distinction between meningiomas and other tumors of the central nervous system occasionally can be difficult. Claudin-1 is a tight junction-associated protein recently shown to be expressed in anaplastic meningiomas. The purpose of this study was to determine whether immunohistochemical staining for claudin-1 could help distinguish meningiomas from histologic mimics, compared with commonly used markers. Tissue sections from 10 meningothelial meningiomas, 20 fibrous meningiomas, 10 atypical meningiomas, 7 solitary fibrous tumors of the meninges, 5 meningeal hemangiopericytomas, and 7 vestibular schwannomas were stained immunohistochemically for claudin-1, epithelial membrane antigen, S-100 protein, CD34, and glial fibrillary acidic protein. In total, 21 (53%) of 40 meningiomas were immunoreactive for claudin-1, whereas none of the other tumors were positive. In contrast, there was considerable overlap in the distribution of the other antibodies evaluated. Claudin-1 seems to be a specific marker for meningiomas in this context. Although its sensitivity is relatively low, claudin-1 may be helpful in a panel of immunostains to distinguish meningiomas from histologic mimics.