RET protein expression has no prognostic impact on the long-term outcome of papillary thyroid carcinoma

Background: RET proto-oncogene rearrangements (RET/PTC) are causative event s in the pathogenesis of a subset of papillary thyroid cancer (FTC). The pr evalence of RET/PTC varies in different countries and according to specific clinical features: it is higher after radiation exposure and it is claimed to be higher in young patients. Conflicting results are reported regarding the prognostic role of RET/PTC activation. Objective: To investigate the prognostic meaning of RET/PTC rearrangement o n the long term outcome of PTC. Methods: We have studied the expression of the RET encoded protein in 127 p apillary thyroid carcinomas by immunohistochemistry using a polyclonal anti body against the tyrosine-kinase domain of the RET protein, These cases hav e been collected during 1970-1985, and have a mean (+/-S.D.) period of foll ow-up of 18.6 +/-3.7 years (range 12-27 years). The results have been compa red with the patients' outcome. Results: The tyrosine-kinase domain of RET was expressed in 82 (64.6%) papi llary carcinomas. Among them, RET was highly expressed in 65 (51.2%) cases and moderately expressed in 17 (13.4%). RET expression was absent in 45 (35 .4%) cases. No correlation was found between RET expression and other param eters such as sex, age at diagnosis, tumor class and histological variant. Follow-up analysis showed no influence of RET expression on patients' outco me. By multivariate analysis, age (> 45 years) and tumor class IV, but not sex and RET expression were adverse prognostic indicators of death. Conclusion: In conclusion, our analysis indicates that RET expression is fr equently found in PTC, and has no influence on tumor outcome.