High prevalence of RET tyrosine kinase activation in Mexican patients withpapillary thyroid carcinomas

RET/PTC oncogene expression is restricted to papillary thyroid carcinomas ( PTC). At least three forms of this oncogene have been described. These are generated by the rearrangement of the 5'-terminal region of different expre ssed genes with the tyrosine-kinase (TK) domain of the ret proto-oncogene. Several studies showing the correlation between the expression of this onco gene, clinical outcome, and histological subtypes have been published. Thir ty-five paraffin-embedded PTC samples from patients without a history of ra diation exposure were studied. Immunohistochemistry (IHC) and in situ hybri dization (ISH) were used to determine a possible correlation between RET ac tivation, clinical outcome, and tumor subtype. Almost half of the studied c ases presented with tumoral extension or metastases. Ret gene transcripts a nd protein were found in all PTC variants as well as in their corresponding metastases. In contrast, none of the follicular adenomas, goiters, or norm al follicular cells from the thyroid gland showed evidence of ret activatio n. We observed a high frequency of ret expression in PTCs, suggesting that ret activation is a common event in nonradiation-related PTC from Mexican p atients.