Heterotopic glial nodules: a light microscopic and immunohistochemical study.

The clinical, light microscopic and immunohistochemical features of 14 heterotopic glial nodules are described. In keeping with previous experience, most cases were located around the nose and had been present since birth. However, several lesions presented as cutaneous nodules elsewhere and, in some, presentation was delayed into childhood or even adulthood. The histological diagnosis is usually uncomplicated, but we draw attention to a variant with a markedly sclerosed stroma in which the glial cells are relatively inconspicuous. Such lesions tend to be found in older subjects and can cause problems in diagnosis. We emphasize the value of immunohistochemical demonstration of glial fibrillary acidic protein in the diagnosis of these lesions, especially in the sclerotic variant. Other immunohistochemical features include the presence of axons in most cases and cell bodies in some, emphasizing the mixed nature of these lesions. A meningeal component could not be demonstrated immunohistochemically, even at the edge of the lesions.