N-RAS MUTATION OF THYROID-TUMOR WITH SPECIAL REFERENCE TO THE FOLLICULAR TYPE

Using the method of polymerase chain reaction-single strand conformati on polymorphism, the point mutations of the ras oncogenes in a total o f 33 thyroid tissues, including 12 follicular adenomas, 6 follicular c arcinomas, 11 papillary carcinomas, and 4 undifferentiated carcinomas, were examined, The frequency of the mutation was 3% (1/33) in codon 1 2, 13 of Ki-ras and 18% (6/33) in codon 61 of N-ras, including 17% (2/ 12) in follicular adenoma, 50% (3/6) in follicular carcinoma, 0% (0/11 ) in papillary carcinoma and 25% (1/4) in undifferentiated carcinoma, In follicular adenoma, positivity was observed in microfollicular or t rabecular subtypes. Furthermore, the mutation of ras was examined in h istologically different parts, coexisting in the same tumor in a total of four cases, Both the undifferentiated carcinoma and coexisting fol licular adenoma, and both the microfollicular adenoma and trabecular n odule growing in the tumor, had the same N-ras (61) mutation, Direct s equencing analysis showed that all mutations were CAA (Gln) to CGA (Ar g) transition of codon 61, except for CAA to AAA transversion in one c ase of follicular carcinoma, A similar genetic abnormality of N-ras ge nes at codon 61 between follicular adenoma and follicular carcinoma su ggests that the mutation of N-ras at codon 61 might play a part in onc ogenesis in follicular tumors.