Squamous cell characteristics in small cell carcinoma of the uterine cervix: histological, immunohistochemical, and ultrastructural study in xenografted small cell carcinoma

Small cell carcinoma of the uterine cervix is a rare type of gynecological tumor that frequently expresses neuroendocrine differentiation. Its histological origin is unclear. We examined the histopathological characteristics of small cell cervical carcinoma in a patient with elevated serum adrenocorticotropin hormone. We then studied the morphological alteration in xenotransplanted tumors (passages 1–9) using immunohistochemistry and electron microscopy. The primary cervical tumor was characterized by a sheetlike arrangement of uniform small cells with hyperchromatic nuclei and a high nucleocytoplasmic ratio. A ribbon-like or trabecular pattern was also observed in a small area of the tumor. Neuron-specific enolase, chromogranin A, and S-100 were positive for the tumor cells, but cytokeratin was negative. Dense-core granules were detected by electron microscopy. In the xenografted tumor, a serial change from squamous cells to round-to-oval cells was observed. Cytokeratin was immunohistochemically stained in the squamous tumor cells but not in the other tumor cells. In contrast, chromogranin A was stained in some of the round-to-oval cells. Basal lamina underlaid the squamous tumor cells, and desmosome-like junctions were apparent. The cytoplasm was filled with well-differentiated organelles including electron-dense tonofilaments. Elliptical tumor cells resembled the primary carcinoma ultrastructurally. These findings suggest that small cell cervical carcinoma with neuroendocrine properties shares the characteristics of squamous cell carcinoma.This study was presented at the 24th Annual Meeting of the Clinical Electron Microscopy Society of Japan, Okayama, September 17, 1992.