Small-cell carcinoma of the endometrium: an immunohistochemical and ultrastructural analysis.

Small-cell carcinoma of the endometrium is a rare neoplasm, and its aggressive behavior has been reported. We report a case of small-cell carcinoma occurring primarily in the endometrium of a 62-year-old woman with postmenopausal vaginal bleeding and lower abdominal pain. The excised uterus showed a necrotic polypoid mass and histologically displayed an endometrial small-cell carcinoma. Immuno-histochemically, the tumor cells were positive for cytokeratin, the epithelial membrane antigen, neuron-specific enolase, and chromogranin, but were negative for the leukocyte common antigen and Grimelius stain. Ultrastructural analysis revealed the presence of dense core granules in the cytoplasm of tumor cells. The patient died 2 months after surgery because of aggressive behavior of the tumor. We wish to distinguish small-cell carcinoma of the endometrium from conventional epithelial tumors of the endometrium, because of the former's distinctive histopathologic, immunohistochemical, and ultrastructural characteristics.