Carcinosarcoma of the esophagus is a rare neoplasm composed of both carcinoma and spindle sarcomatous area. Usually the carcinoma component is a squamous cell carcinoma but rarely adenocarcinoma or undifferentiated carcinoma is found. The histogenesis of the sarcomatous component is still unknown. A case of ulcerated polypoid lesion with a stalk in esophagus was reported. Microscopically it was composed of spindle shaped cells interminled with squamous cell carcinoma and small cell carcinoma nests. No distinct transition between spindle shaped cells and carcinoma are was observed. Immunoreactivity to cytokeratin was observed in both carcinomatous and spindle cell component, but electron microscopic examination failed to demonstrated desmosome or tonofilaments in spindle cells. Undifferentiated small cell nests were reactive to neuron specific enolase and contained membrane bounded secretory granule in electron microscopy.