CARCINOSARCOMAS OF THE ESOPHAGUS

Two cases of carcinosarcoma of the esophagus are reported. Both were p olypoid tumors occurring in the middle of the intrathoracic esophagus. The tumors were predominantly composed of spindle-shaped sarcoma cell s with some squamous cell carcinomas (SCC). One tumor showed many biza rre giant cells with filamentous materials in the cytoplasm. Microscop ical examination of both tumors revealed transition from SCC to sarcom a cells, Immunohistochemically, the spindle-shaped sarcoma cells in bo th tumors displayed a strongly positive immunoreaction to alpha-smooth muscle actin, as did the bizarre giant cells of one tumor to sarcomer ic actin, SCC and a few spindle-shaped sarcoma cells near the SCC show ed a positive immunoreaction to cytokeratin. Electron microscopy revea led that the spindle-shaped cells had many myofilaments with dense bod ies and that the bizarre giant cells had sarcomere structures with Z-b ands in their cytoplasm. These findings indicate that both tumors were carcinosarcomas of SCC and myogenic sarcoma. We considered that sarco ma cells might originate in SCC, representing its metaplastic differen tiation, or that both SCC end sarcoma might originate in a pluripotent stem cell.