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%).
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.