[Demonstration of activated oncogenes of the ras family in human thyroid tumors using the polymerase chain reaction].

Activation of ras-oncogenes in 180 different thyroid tumours, was examined by using polymerase chain reaction (PCR) amplification and subsequent analysis of the amplification products by oligonucleotide probing, direct sequence analysis of single stranded DNA and primer-mismatch analysis. In contrast to recently published results we found a very low frequency of activated ras-genes occurring mainly in undifferentiated carcinomas and follicle cell carcinomas which show a transition to undifferentiation. In none of thirty benign tumors an activated ras-gene was found. The predominant ras-oncogene activated in thyroid neoplasias was the Harvey-ras gene. Our results suggest Harvey-ras activation at a later evolutionary step in tumour genesis.