Small cell carcinoma of the endometrium in a 23-year-old woman: light microscopic and ultrastructural study.

The case of a 23-year-old woman with a primary small cell carcinoma of the endometrium is reported. The light microscopic features were similar to those of small cell carcinoma of the lung and those of the uterine cervix. Electron microscopy revealed cytoplasmic neurosecretory type granules and indistinct cell junctions, features characteristic of neuroendocrine cells. The neoplasm behaved in a very aggressive manner, similar to that of small cell carcinoma of the lung and quite unlike that of the usual endometrial adenocarcinoma. Small cell carcinomas of the endometrium with neurosecretory type granules may have a worse prognosis than better differentiated endometrial adenocarcinoma with argyrophilic granules and thus may require adjuvant radiotherapy or chemotherapy or both.