PCR amplification and analysis of ras oncogenes from thyroid cytologic smears

Fine needle aspiration (FNA) cytology represents a reliable diagnostic procedure for preoperative identification of thyroid carcinoma. For improving its diagnostic accuracy, a technique that allows the analysis of cancer-related gene abnormalities on thyroid FNA smears has been developed. Cells were collected by scraping from thyroid smears, DNA-extracted and ras proto-oncogene sequences amplified by the polymerase chain reaction (PCR). Preliminary destaining of cytologic smears was essential for efficient PCR amplification. Twelve thyroid FNA cytologic smears, characterized by the indeterminate pattern of follicular neoplasia, were analysed for the presence of ras mutations known to confer an oncogenic potential. The same nucleotide substitution at codon 12 of the H-ras proto-oncogene was detected in two different thyroid nodules among six cases that, at final histology, were identified as follicular carcinomas. No ras mutations were observed in the remaining six cases that were diagnosed as follicular adenoma at histologic examination. Molecular analysis of FNA smears may provide additional information on the nature of the lesion underlying thyroid neoplasia, thus improving diagnostic accuracy of conventional FNA cytology.