OBJECTIVETo evaluate the expressions of wildtype-RET (WT-RET) and RET/PTC in sporadic adult papillary thyroid carcinoma and to investigate their clinicopathologic correlation.

METHODSSixty-six papillary thyroid carcinomas (PTC) and thirty-six control cases with frozen and paraffin-embedded tissues were analyzed for the expressions of WT-RET and oncogene RET/PTC1 or RET/PTC3 by nested RT-PCR.

RESULTS(1) 62 percent (41/66) of PTC patients were above 40 years of age. Thirty-eight percent (25/66) of the tumors showed lymphocytic thyroiditis. Lymph node and distant metastasis were seen in 59% (39/66) and 7.6% (5/66) respectively. (2) Forty-five cases (68.1%) of PTCs expressed RET tyrosine kinase domain (RET-TK). Simultaneous expressions of RET-BP and TK were seen in nineteen PTCs (28.8 %). One of eight adenomas (12.5 %) expressed wild-type RET (WT-RET). (3) Fourteen PTCs (21.2%) expressed RET/PTC, including five cases expressing RET/PTC1 and nine cases expressing RET/PTC3. Six cases (9%) expressed both RET/PTC and WT-RET. (4) Statistic analysis did not show any correlation between the expression of WT-RET or RET/PTC and clinicopathologic parameters.

CONCLUSIONSThe expression of RET/PTC was specific to PTC. However, its prevalence was low and, therefore, of limited diagnostic utility. The expression patterns of WT-RET in PTC and adenoma suggest that there are different molecular mechanisms in activating RET proto-oncogene in thyroid tumors.