The vast majority of tumors of the pancreas are ductal adenocarcinomas. This cancer type has an extremely poor prognosis and in many Western countries, it represents the fifth leading cause of cancer-related death. Pancreatic ductal adenocarcinomas exhibit the highest incidence of activating KRAS (Ki-Ras) mutations observed in any human cancer. It was therefore of interest to examine how this pattern would relate to mutations in the BRAF and EGFR genes, which are involved in the same signaling pathway as KRAS. We screened a series of 43 formalin-fixed, paraffin-embedded ductal adenocarcinomas of the pancreas. When DNA was extracted from whole tissue sections, KRAS codon 12 mutations were detected in 67% of the tumors. When cancerous ducts were isolated by laser-assisted microdissection, 91% were positive for KRAS mutations. Although it did not reach statistical significance, there was a trend in our material that survival after diagnosis varied according to KRAS mutation subtype, GTT-positive patients having the best prognosis. No alterations in BRAF exons 11 and 15 or in EGFR exons 18-21 were detected in KRAS-positive or KRAS-negative cases. We therefore conclude that the BRAF and EGFR mutations commonly seen in a variety of human cancers are generally absent from pancreatic ductal adenocarcinomas. Apparently, these tumors depend on no more than one genetic hit in the EGFR-RAS-RAF signaling pathway.

Our objective was to investigate the practicability of sequencing DNA from formalin fixed, paraffin embedded tissue stored for up to 75 years and to study human papillomavirus subtype distribution in cervical neoplasias between 1931 and 2004. Three protocols for DNA retrieval were tested, and magnetic bead DNA extraction proved advantageous, as it gave superior specimen purity and effortless sequencing. Successful sequencing was achieved in more than 70% of the specimens from 1931 to 1960. This technique was utilized in the study of papillomavirus subtypes using general primer pair PCR with sequencing of the products in a series of 97 cases of neoplastic and non-neoplastic cervical specimens from 1931 to 1960 and 73 similar cases from 1992 to 2004. HPV was detected in 61% of neoplastic specimens from 1931 to 1960, and in 89% of those from 1992 to 2004. In specimens from 1931 to 1934, only HPV type 16 was detected, whereas in the specimens from 1940 and up, other HPV subtypes were identified in one-third of the cases. The difference was significant and suggests an increase in papillomavirus subtype heterogeneity in Western Norway during 1930-2000. The results strongly support the feasibility of using DNA from paraffin-embedded specimens for studying cancer etiology and genotypes over extended time periods.