Background: Persistent descending mesocolon (PDM) is a rare colonic anatomical variant. However, PDM's impact on the technical aspects and outcomes of laparoscopic colorectal cancer resection are unclear. Patients and Methods: This retrospective clinical cohort study was conducted at a high-volume cancer center in Japan to evaluate intra-and postoperative outcomes of laparoscopic colorectal cancer surgery in patients with (PDM+) or without (PDM-) PDM over the past 7 years. Results: Between January 2012 and September 2019, 2,775 patients underwent laparoscopic colorectal cancer resection at our center, including 60 (2.1%) cases of PDM. Preoperative detection was achieved in only 5 patients (8.3%), 39 patients were men, and 21 patients were women. The average age was 67 years. Twenty patients had a history of prior abdominal surgery (33.3%), with little or no subsequent adhesions. The average duration of sigmoidectomy in PDM+ patients (n=17; 217.7±14.2 min) was significantly longer than that in 176.2±2.4 min; p=0.003), as was average blood loss (32.3±10.6 ml vs. 16.7±2.8 ml; p=0.03). Likewise, average operative time for high anterior resection in PDM+ patients (n=11; 227.1±20.2 min) was significantly longer than that in 195.6±3.0 min; p=0.048). Rates of postoperative anastomotic leakage and postoperative recurrence did not differ in both groups. In PDM+ patients, retention of left colic artery had no impact on proximal specimen margins or occurrences of anastomotic leakage. Conclusion: PDM prolongs operative times and increases bleeding in laparoscopic colorectal cancer surgery and should be considered a risk factor when encountered.

Background/Aim: The purpose of this study was to investigate the clinical, pathological, and prognostic differences between adenocarcinoma (ADC) and mucinous adenocarcinoma (MUC) in colorectal cancer (CRC). Patients and Methods: This was a retrospective study of a Japanese high-volume cancer Center over a 10-year period. From April 2007 to December 2016, a total of 3,296 patients with primary CRC were included in the study. The clinical characteristics of MUC and ADC were compared. Then, propensity score matching was performed according to a 1:2 ratio. Multivariate analysis was used for independent risk factors related to prognosis. The overall survival (OS) and disease-free survival (DFS) of 126 cases of MUC and 256 cases of ADC were studied, as well as the survival rate of each stage. Results: MUC accounts for 3.82% of the total CRC. Compared to ADC, MUC is more common in female patients (47.62% vs. 38.77%; p=0.045), with higher carcinoembryonic antigen levels (56.35% vs. 34.95%; p<0.001), more ulcerative and infiltrative types (82.54% vs. 72.93%; p=0.016), higher incidence of perineural infiltration (51.59% vs. 41.04%; p=0.018), deeper infiltration (T3-T4: 90.48% vs. 65.84%; p<0.001), and more advanced cancer (stage III-IV: 59.52% vs. 44.79%; p=0.001). MUC is also more likely to recur (24.6% vs. 14.32%; p=0.001). Regarding the long-term survival rate, the OS (p<0.001) and DFS (p=0.05) is consequently worse. After propensity score matching, multivariate analysis showed that MUC was a common independent risk factor for DFS [odds ratio (OR)=4.277; 95% confidence interval (CI), 0.327-0.97; p=0.039], and also for OS (OR= 6.836; 95% CI, p=0.009). In MUC, OS and DFS were still relatively worse (OS: p=0.017; DFS: p=0.038). However, only significant statistical differences were shown in stage II (OS: p=0.003; DFS: p=0.007). No significant differences were noted in the stages I, III, or IV. Conclusion: MUC is a high-risk factor for stage II CRC. Adjuvant chemotherapy should be routinely recommended for patients with MUC stage II, and special attention should be paid during their follow-up.According to European and American guidelines, patients with a high risk of recurrence after radical surgery for stage II colorectal cancer (CRC) should receive adjuvant chemotherapy (1, 2). However, the definition of "high risk" varies. Mucinous adenocarcinoma (MUC) is defined as a high-risk factor in United States guidelines, but not in European guidelines. In Japan, clinical trials of conventional postoperative adjuvant chemotherapy for stage II CRC have not been found to be successful (3). In 2019, there are few Japanese guidelines for the treatment of stage II rectal cancer using adjuvant chemotherapy (4). There are also different opinions on whether or not adjuvant chemotherapy is required for patients with postoperative stage II MUC.MUC is a rare tumor classification of CRC. This type of tumor contains neoplastic cells that produce a large amount of extracellular mucin. Histological markers require more than 50% of the tumor...

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Background: Unlike the tumor nodes metastasis (TNM) lymph node classification, based solely on counts of nodal metastases, the Japanese system of classifying colorectal carcinoma (CRC) focuses on regional lymph node spread. In this study, we explored the prognostic utility of inferior mesenteric artery (IMA) apical lymph node (APN) metastasis. Patients and Methods: This was a retrospective study of patients with stage III left-sided CRC. All enrollees were subjected to D3 resection between April 2007 and December 2016 at the International Medical Center of Saitama Medical University and then stratified by histologic presence (APN+ group) or absence (APN− group) of tumor in APNs examined postoperatively. Ultimately, propensity score matching was invoked (1:2) and COX regression analysis was conducted, determining group rates of relapse-free survival (RFS) and cancer-specific survival (CSS). Results: A total of 498 patients were studied, grouped as APN+ (19/498, 3.8%) or APN− (479/498, 96.2%). Prior to matching, the APN+ (vs. APN−) group showed significantly more lymphatic involvement (73.7% vs. 47.8%; p=0.023), deep (T3/T4) tumor infiltration (100% vs. 78.9%; p=0.024), and nodal metastasis (N2: 84.2% vs. 27.6%; p<0.001). In addition, para-aortic nodal recurrences were significantly increased (15.7% vs. 2.0%; p<0.001), conferring worse RFS (p<0.001) and CSS (p=0.014) rates. Once baseline factors were matched, the two groups appeared similar in RFS (p=0.415) and CSS (p=0.649). Multivariate regression analysis indicated that elevated carcinoembryonic antigen (CEA) level and deep tumor infiltration were independent risk factors for RFS, whereas postoperative complications and tumor-positive node counts were independent risk factors for CSS. APN+ status was not a significant risk factor for RFS or CSS. Conclusion: APN positivity may thus constitute a regional rather than systemic manifestation. The TNM staging based on the number of metastatic lymph nodes seems to be more reasonable than the regional lymph node classification method. Patients and Methods As candidates for this retrospective analysis, a total of 2,457 patients underwent surgical resections of left-sided CRC at the International Medical Center of Saitama Medical University between April 2007 and December 2016. Exclusion criteria were as follows: 1) recurrent 2981 This article is freely accessible online.

Background/Aim: The purpose of this study was to explore the perioperative, short-term, and long-term prognostic differences in colorectal cancer (CRC) between young and older patients. Patients and Methods: A total of 3095 patients were divided into young (≤45 years; n=139) and older (>45 years; n=2956) groups. Then, propensity score matching was performed for patients in stage I to III according to a ratio of 1:1. The clinicopathological factors and prognosis of the two groups were studied. Results: Young patients with CRC account for 4.49% of the total number of patients with CRC. Younger patients with CRC in stage I to III showed better cancer-specific survival (CSS). Older age was an independent risk factor for CSS prognosis. The CSS of the younger group was significantly better in stage I to III as a whole, but there was no difference in stage I and II subgroups -only in stage III. The proportion of young patients with stage III disease receiving first-line adjuvant chemotherapy was significantly higher. When young patients relapsed, they were more likely to receive second-line adjuvant chemotherapy or reoperation than older patients. Conclusion: Younger patients with stage III colorectal cancer had better CSS rates.

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