Primary neuroendocrine carcinoma of the eyelid, immunohistochemical and ultrastructural study.

Primary neuroendocrine carcinomas of the skin were recognized as distinctive neoplasms and clinicopathologic information on their location on the eyelids have been reported. The authors present one case of primary neuroendocrine carcinoma occurring on the right lower lid in a 73-year-old woman. The clinical history, light and electron microscopic findings as well the results of an immunohistochemical study are described. The ultrastructural study demonstrated the characteristic membrane-bound dense-core neurosecretory granules. Immunoreactivity for neuron-specific enolase, keratin filaments, epithelial membrane antigen and calcitonin were observed and are strongly suggestive of a neuroendocrine differentiation in a neoplasm of epithelial origin. Various hypothesis concerning the origin of this tumor are discussed on the basis of the immunohistochemical findings. The authors also provide a brief review of the literature.