MOLECULAR MARKERS FOR DIAGNOSTIC CYTOLOGY OF NEOPLASMS IN THE HEAD REGION OF THE PANCREAS - MUTATION OF K-RAS AND OVEREXPRESSION OF THE P53PROTEIN PRODUCT

Aims-To determine the potential efficiency of molecular markers specif ic for neoplastic change-mutations of the K-ras oncogene and the p53 t umour suppressor gene-in diagnosing pancreatic carcinoma. Methods-Arch ival cytology samples obtained from 17 patients with established pancr eatic carcinoma were assayed for alterations in K-ras and p53. To dete ct changes in p53 expression, immunocytochemistry with polyclonal anti body CM1 was performed on the archival cytology slides after destainin g. Mutations in K-ras codon 12 were then analysed on the scrapings of the same slides using mutant enriched polymerase chain reaction (PCR) amplification and restriction fragment length polymorphism analysis wi th oligonucleotide hybrid-confirmation and characterisation. Results-F alse negative results were recorded for five of the cytology slides wh en compared with p53 immunostaining of the surgical resection specimen . These five cases had been stained previously with Giemsa which inter acts adversely with the immunostaining in contrast to the Papanicolaou procedure. The K-ras codon 12 mutations followed the well distributio n frequency and for pancreatic cancer and corresponded with the findin gs in the resection specimens in all cases. Two scrapings yielded insu fficient DNA for PCR. Importantly, for two cases with an inconclusive cytology diagnosis on routine Light microscopy, the diagnosis was conf irmed by one of the molecular markers. The application of the molecula r markers increased the diagnostic accuracy of cytology in this small study from 76 to 89%. Conclusions-The study indicates that assessment of alterations in the K-ras and p53 genes may be a valuable adjunct to diagnostic cytopathology of the head region of the pancreas, although there are some difficulties which will have to be overcome.