Vacuum-based preservation of colorectal cancer specimens: A comparison with formalin fixation J.-F. Fléjou * , S. El-Naderi, P. Cervera * Hôpital Saint-Antoine, Dept. de Anatomie Pathologique, Paris, France Objective: In Pathology, an alternative to immediate fixation in neutral buffered formalin (NBF) is vacuum sealing and cooling (VSC) ("Tissue safe" system). There have been few evaluations of VCS. Method: We assessed MSI, KRAS, BRAF in colorectal cancers, conserved with VCS before fixation (51 cases with surgery in a hospital distant from our centre), or immediately fixed in NBF (56 cases with surgery during the same period in our hospital). DNA was extracted from paraffin embedded tissue. MSI was assessed by MLH1 and MSH2 immunohistochemistry and PCR; KRAS and BRAF were screened by multiwell-plate based real-time PCR (LightCy-cler® 480, Roche), confirmed by Sanger sequencing. Results: There was no difference regarding morphological analysis. Immunohistochemistry was interpretable in all cases, with 4 negative cases in the VCS group (4 MLH1), 11 negative cases in the NBF group (10 MLH1, 1 MSH2), and a 100 % correlation between immunohistochemistry and PCR. DNA extraction was possible in all cases. KRAS and BRAF mutations were detected in 21 and 1 cases in the VCS group and 16 and 7 cases in the NBF group, respectively. Conclusion: We show that analysis of MSI, KRAS and BRAF is feasible in surgical specimens after VCS. This procedure can be an alternative to formalin fixation.