Granular cell tumor of the orbit and ocular adnexae.

Although granular cell tumor (GCT) has been a distinct pathological entity since 1926, confusion and controversy have long existed regarding the nature and histogenesis of the tumor. Twenty-five cases of granular cell tumor involving the orbit and ocular adnexae previously reported in the ophthalmic literature, are reviewed and six additional cases are reported. The histopathological and immunohistochemical characteristics of granular cell tumors in this uncommon location are discussed and their probable origin from Schwann cells is also considered.