Lynch syndrome is a hereditary colorectal cancer syndrome caused by mutations in the DNA repair system genes. We studied the clinical and genetic characteristics of 27 Russian patients with Lynch syndrome. Germinal mutations were found in genes MLH1 (14 patients), MSH2 (11 patients) and MSH6 (2 patients). Eight mutations have not been described previously. The clinical features of this group of patients consisted of early average age of the first cancer - 36.7 years, predominant (72.4%) damage of the left colon, occurs most (70.6%) metachronous tumors for 10 years after the previous surgery, high (53.6%) frequency of poorly differentiated adenocarcinomas. The described genetic and phenotypic pattern indicates a need for more targeted selection of patients with suspected Lynch syndrome as well as the feasibility of the development of clinical guidelines for monitoring and surgical treatment exactly Russian patients.

To determine mutations in the plasma KRAS gene in patients with colorectal cancer was the aim of this study. The material was obtained from 44 patients with colorectal cancer of different stages (T1-4N0-2bM0-1c). Plasma for the presence of KRAS gene mutation in circulating tumor DNA was investigated using digital droplet polymerase chain reaction (PCR). KRAS mutations in circulating tumor DNA isolated from 1 ml of plasma were detected in 13 (30%) patients with cancer of different stages. Of these, with stage II, there were 3 patients, with III - 5 and with IV - 5. Patients who did not have mutations in 1 ml of plasma were analyzed for mutations of KRAS in circulating tumor DNA isolated from 3 ml of plasma. Five more patients with KRAS mutations were found with II and III stages. The highest concentrations of circulating tumor DNA with KRAS mutation were found in patients with stage IV. The increase in plasma volume to 3 ml did not lead to the identification of mutations in I stage. This study showed that digital droplet PCR allows identification of circulating tumor DNA with the KRAS mutations in patients with stage II-IV of colon cancer. The results can be used to determine the degree of aggressiveness of the tumor at different stages of the disease, but not the 1st, and it is recommended to use a plasma volume of at least 3 ml.

Objective: Rectal neuroendocrine tumors (NETs) are rare neoplasms and, therefore, few clinical observational studies have been performed and few publications are available on this matter. With regard to the aforesaid, it seems topical to analyze and publish results of local rectal NET excisions that were performed at Federal State Budgetary Institution «State Scientific Centre of Coloproctology n.a. A.N. Ryzhikh» of the Ministry of Healthcare of Russia. Patients and methods: Within the period from December 2011 until June 2018 14 patients, including 4 (28.6%) men and 10 (71.4%) women underwent transanal endoscopic microsurgery (TEM) for rectal NETs at Federal State Budgetary Institution «State Scientific Centre of Coloproctology n.a. A.N. Ryzhikh» of the Ministry of Healthcare of Russia. The mean age of the patients was 53.2 ± 14.14 (24 to 74) years old. Remote results of the treatment performed were traced for all 14 (100%) patients. Kaplan-Meier curves were graphed and then compared using the log-rank (Mantel-Cox) method. Results: On the basis of findings of pathomorphological studies, 10 (71.4%) patients were diagnosed with stage pT1a tumors, 3 (21.4%) participants had stage pT1b tumors, and 1 (7.2%) patient had stage pT2 tumor; 11 (78.6%) patients enrolled to the study had G1 tumors and 3 (21.4%) participants had G2 tumors; and lymphovascular invasion was detected in 4 (28.5%) of the 14 patients. All excisions were radical (R0). The median follow-up period was 25.5 (9 to 86) months. Disease progression was found in 3 (21.4%) of the 14 patients. NET size exceeding 10 mm was the only statistically significant factor that had impact on relapse-free survival (p=0.032). Conclusion: Local excision of rectal NETs can be an option of surgical treatment for small (< 10 mm) low-grade tumors. At the same time, precision and safety are of unquestionable priority in TEM.