Studying the molecular pathology of cytological samples from pancreatic and biliary ducts

Abstract

Despite general development in cancer diagnostics pancreatic cancer remains one of the cancers with the poorest prognosis. The diagnosis is usually done in a late stage as reliable screening methods are not available. Resection increases the five year survival rate from 5% to 20% but only one in five pancreatic cancers is detected when the surgical resection is still possible. KRAS mutation is present in almost all cases and TP53, CDKN2A and SMAD4 mutations are common (40-60% of cases). A cytological brush sample can be obtained from pancreatic and biliary ducts. The sample is usually low in cellularity and microscopic diagnosis alone may be inconclusive. The inclusion of molecular pathology methods could clarify the diagnosis. The aim of this Master's Thesis was to study if pancreatic cancer associated mutations were detectable from the cytological samples and to evaluate the value and sensitivity of the molecular diagnostic methods used. 30 cytological samples from pancreatic and biliary ducts of pancreatic cancer patients were studied with droplet digital PCR (ddPCR) and next generation sequencing (NGS). KRAS mutation was detected in 63,3% with ddPCR and 57% with NGS. With NGS a mutation in TP53, CDKN2A and SMAD4 was found in 60%, 40% and 30% of the cases, respectively. In conclusion, the sensitivity of ddPCR was higher than NGS but neither were highly sensitive when studying KRAS mutation from samples with low tumor DNA yield. KRAS mutation was found to be unspecific for malignancy as it was found from 33% of 24 benign control samples studied with ddPCR. TP53, CDKN2A, and SMAD4 were detected with similar frequency than in literature when using NGS. Cytological samples hold potential for diagnostic use when suitable biomarkers and sensitive methods are used.