Clonality Study in Carcinosarcomas and Malignant Mixed Epithelial Tumors

ABSTRACT

BACKGROUND: Tumors are usually considered to be clonal progeny of single transformed cells. Carcinosarcomas and malignant mixed epithelial tumors are examples where controversies exist regarding the singularity or multiplicity of their cell of origin. METHODS: The authors examined the clonality of carcinosarcomas (7 cases) and malignant mixed epithelial tumor (5 cases) in female patients by X-chromosome inactivation as a marker. Each component of the tumors were picked up by the laser capture microscope. The polymorphic exon 1 CAG trinucleotide repeat in the X-linked human androgen receptor (HUMARA) gene was amplified by a polymerase chain reaction before and after treatment of the methylation-sensitive endonuclease HpaII. RESULTS: Eleven cases were informative for clonality determination. Six out of seven carcinosarcomas and three out of four malignant mixed epithelial tumors revealed the same patterns of X-chromosome inactivation, which suggests that they are monoclonal. In contrast, the patterns of X-chromosome inactivation were different between the two tumor components in each cases of carcinosarcoma and malignant mixed epithelial tumor, indicating that they are of polyclonal origin. CONCLUSIONS: These observations show that although most of carcinosarcomas and malignant mixed epithelial tumors are of monoclonal origin, some of them are of polyclonal origin. This finding suggests that these tumors are genuinely polyclonal, and that they originated in the neoplastic transformation of more than one somatic cells