Esophageal carcinosarcoma: a genetic analysis.

Carcinosarcoma of the esophagus is a rare malignant neoplasm that consists of both carcinomatous and sarcomatous elements. The histogenesis of the sarcomatous component is generally considered to result from metaplasia of carcinomatous cells toward mesenchymal differentiation. True carcinosarcoma, characterized as a collision between a carcinoma and a sarcoma, is extremely rare. We describe a patient with primary achalasia who developed a true carcinosarcoma of the esophagus in which clonal differences between carcinomatous and sarcomatous elements were genetically and immunohistochemically demonstrated. A polypoid tumor located in the middle third of the esophagus developed in a 51-year-old man with longstanding achalasia. The tumor was predominantly composed of spindle-shaped sarcomatous cells. Squamous cell carcinoma in situ and islands of well-differentiated squamous cell carcinoma in the sarcomatous element were histologically observed. The sarcomatous element was immunoreactive for both mesenchymal and myoid markers. The carcinomatous component expressed type I and type II cytokeratins as well as epithelial membrane antigen. Analysis for chromosomal loss of heterozygosity performed in multiple microdissected samples of each sarcomatous and carcinomatous element revealed distinct genetic clonalities. These differences in immunohistochemical and genetic clonalities suggest that the tumor composed of squamous cell carcinoma and leiomyosarcoma originated separately from epithelial and mesenchymal precursors.