Intracranial inflammatory pseudotumor.

An intracranial mass thought clinically and by computed tomography and angiography to be a meningioma proved to be an inflammatory pseudotumor. The lesion was composed of sheets of mature plasma cells and lymphocytes with germinal center formation. Immunohistochemical studies revealed a polyclonal cell population, supporting a diagnosis of a reactive lesion rather than a plasma cell neoplasm. Inflammatory pseudotumor should be considered in the differential diagnosis of a sharply demarcated intracranial mass clinically and radiologically diagnosed as meningioma.