Direct sequencing analysis showed that all mutations were CAA (Gln) to CGA (Arg) transition of codon 61, except for CAA to AAA transversion in one case of follicular carcinoma.
Activating point mutations in the N-ras gene (nine CAA (Gln) to AAA (Lys) transversions and one CAA (Gln) to CGA (Arg) transition at codon 61) were detected at high frequency (56%).