The general prevalence of RET/PTC rearrangement in thyroid PDC and its impact on patient outcome are unknown.     ///    "RET/PTC rearrangement, analyzed by RT-PCR and immunohistochemistry using antibodies specific for the tyrosine kinase and juxtamembrane portions of the RET protein, was identified in 8/62 (12.9%) PDCs. "    ///    "RET/PTC was more common in cases with histologic evidence indicating coexistence with or possible evolution from a well differentiated papillary carcinoma (5 of 25 tumors, 20%) but did not correlate with other clinicopathologic parameters. "    ///    The relatively low prevalence of RET activation in PDCs argues against a major role for RET/PTC in the progression from well to poorly differentiated thyroid tumor phenotypes. 