Abstract

This report describes a very rare case of primary undifferentiated carcinoma of the endometrium with small cell and trophoblastic differentiation. The patient was 54-year-old woman with complaints of vaginal bleeding and palpable lower abdominal mass. The light microscopic findings revealed predominantly small cells with round nuclei, spindle cells, and large cells with hyperchromatic bizarre nuclei. Foci of syncytiotrophoblastic giant cells are scattered, especially in the hemorrhagic areas. Immunohistochemical stainging for neuron specific enolase and beta-hCG showed positive reactions to small cells and syncytiotrophoblastic giant cells, respectively. Argentaffin and argyrophil stains, however, showed negative reactions to small cells. The histogenesis of small cell undifferentiated carcinoma of the endometrium remains unclear; however, it may arise from epithelial precursors instead of neuroendocrine cells, and syncytiotrophoblastic cells may be differentiated or dedifferentiated from the undifferentiated carcinoma cells.

• Keywords: Endometrial undifferentiated carcinoma;small cell carcinoma;and syncytiotrophoblastic differentiation