Neuroendocrine tumors of the ovary--a review.

Neuroendocrine tumors are a heterogeneous group of separate clinico-pathological entities which have a common characteristic i.e. expression of endocrine differentiation potential. In the ovary, the term "neuroendocrine" relates mainly to widely known carcinoids, but it may also be applied to rare neuroendocrine carcinomas of non-small-cell type and small cell carcinomas of pulmonary type. Ovarian carcinoids develop in pure form or in association with other tumors, mainly teratomas. They originate from endocrine cells, either of teratomatous origin or possibly also indigeneous. Ovarian neuroendocrine carcinomas belong most probably to surface epithelial neoplasms, which express endocrine pathway of differentiation. The neuroendocrine carcinomas of non-small-cell type are characterized by the presence of islands, sheets, and trabeculae with little intervening stroma (organoid growth pattern) and cellular homogeneity. However, they are higher-grade than carcinoids. To date, eight ovarian neuroendocrine carcinomas have been described, and all developed in association with glandular müllerian type component. The neuroendocrine differentiation was confirmed by presence of at least two specific markers (argyrophilia and/or argentaffinity, chromogranin A). Initial observations suggest that the presence of neuroendocrine differentiation carries bad prognosis. Primary ovarian small cell carcinomas of the pulmonary type do not differ histologically from their counterparts in other organs. They are composed of small cells with scanty cytoplasm and oval to spindle-shaped nuclei. About 13 cases of this tumor type in the ovary have been reported. Some of them developed in pre-existing benign or malignant ovarian tumors. Argyrophilia and positive chromogranin A staining were seen in two cases only. The prognosis for this tumor type is poor.