Selective activation of ras oncogenes in follicular and undifferentiated thyroid carcinomas

A total of 96 tumour samples (88 primary tumours and 8 nodal metastases) from 88 patients with thyroid adenomas and carcinomas were investigated for ras gene mutations using polymerase chain reaction, oligonucleotide probing and sequencing. Neither the 19 adenomas nor the 31 papillary carcinomas analysed harboured point mutations. In our cases, mutations in all three ras oncogenes were found in follicular carcinomas (five out of 21) and in the less differentiated thyroid tumour: poorly differentiated carcinomas (three out of 11) and undifferentiated carcinomas (one out of five). Finally, mutated ras oncogenes had a significant association with the appearance of haematogenous (particularly bone) metastases, suggesting a role of ras genes activation in the metastatic capability of these tumours.