The roles of ret/PTC fusion genes in thyroid papillary carcinoma

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Background: The activation of ret proto-oncogene, through chromosomal translocation, is reported as unique to papillary thyroid carcinomas. However, the prevalence of RET/PTC activation in papillary carcinoma reported was variable and the clinical relevance of RET/PTC rearrangements in papillary carcinomas is still controversial.Methods: To investigate the roles of ret rearrangement in the carcinogenesis of papillary thyroid carcinoma, we have studied ret activation and p53 overexpression in various thyroid lesions of Japanese population by immunohistochemical technique.Results: Ret activation and p53 overexpression were studied in 40 papillary carcinomas, 5 poorly differentiated carcinomas, 1 undifferentiated carcinoma, 2 medullary carcinoma, 2 follicular carcinomas, 19 follicular adenomas. RET activation was observed in 12 out of 40 papillary carcinomas, while no immunoreactivity of ret was detected in other lesions. P53 overexpression was observed in only one of 40 papillary carcinomas.Conclusion: The prevalence of RET/PTC activation in papillary carcinoma among Japanese population was higher than previous reports. Immunohistochemistry is proved as a useful tool to detect RET/PTC activation in thyroid tumors. RET rearrangements are restricted to a well-differentiated papillary carcinoma, suggesting that RET/PTC positive papillary carcinomas do not progress to undifferentiated carcinoma.