Differential mutation patterns of KRAS and BRAF in adenomatous and serrated neoplastic sequences O. Erdogan * , B. Savas, A. Ensari * Ankara University, Faculty of Medicine, Turkey Objective: Colorectal carcinomas develop through adenomatous or serrated neoplastic sequence. Different molecular mechanisms underly these morphologic sequences which may be translated into different therapies. We aimed to assess adenomatous and serrated neoplastic sequences in terms of KRAS and BRAF mutations. Method: The study group comprised of adenomatous polyps (APs, n=20, 13.6 %), conventional adenocarcinomas (ConCA, n = 30, 20.4 %), serrated polyps (SPs, n = 67, 45.6 %) and mucinous adenocarcinoma (MucCA, n=30, 20.4 %). KRAS mutation was assessed for exon 2 and exon 3 using pyrosequencing while BRAF V600E mutation was analysed using allele specific PCR. Chi square test was used for statistics. Results: KRAS mutations were observed in 41.5 % of carcinomas and 25.3 % of polyps. KRAS mutation rate was significantly higher (p<0.05) in ConCA (85 %) than in MucCA (50 %), and in APs (55 %) than in SPs (16.4 %). BRAF mutation was found in one MucCA (1.7 %) while all SPs were mutated. TSAs had the highest KRAS mutation rate (36.8 %) in comparison to SSA/Ps (17.6 %) (p<0.001) whereas SSA/Ps and HPs had significantly higher rates of BRAF mutation (64.7 %, 61.1 %, respectively) than TSAs (26.3 %) (p<0.001). Conclusion: KRAS seems to take part in adenomatous sequence while BRAF, seem to play a significant role in serrated neoplastic progression of the colorectum. Objective: Quiescent ulcerative colitis (Q-UC) is morphologically characterized by typical architectural and cellular mucosal changes that define the process as chronic. It is not clear which of these changes are more ubiquitous in Q-UC. Our aim was to evaluate which classical histological findings of Q-UC are more prevalent in rectal samples. Method: Rectal biopsies were collected from patients with clinical and endoscopical Q-UC. The biopsies were evaluated for mixed inflammation in the lamina propria, crypt architectural abnormalities, basal plasmacytosis, fibrosis, and Paneth cell metaplasia as well as for features of active disease (cryptitis, lamina propria neutrophils and erosion). Results: Forty-five patients (64 % female; median age 56 years) were included. Thirteen (28,9 %) biopsies showed focal activity and four cases (8,9 %) had criteria for active disease. Epithelial distortion, chronic inflammatory infiltrate and basal plasmacytosis emerged as features present in 95, 81 and 73 % of biopsies. Overall, 4 biopsies were histologically normal (no chronic features, no active disease). Conclusion: Rectal mucosa from patients with clinical and endoscopical Q-UC can show microscopic active disease, which illustrates that endoscopy alone may be insufficient to identify quiescent disease. In Q-UC, the most frequent changes (present in over 75 % of the biopsies) were epithelial distortion and chronic inflammatory infiltrate.