Introduction 1 2 6 7 Materials and methods Between August 2004 and November 2007, the medical records of all patients who underwent laparoscopic surgery for colorectal cancer were reviewed. Laparoscopic colorectal cancer resection was started August 2004 in our clinic. Pathologic confirmation, colonoscopy, barium enema, computed tomography (CT), ultrasonography, and chest PA were performed for diagnosis in all patients preoperatively. All patients with colorectal adenocarcinoma admitted to our clinic were considered for laparoscopic surgery. Exclusion criteria for laparoscopic surgery were as follows: (1) patients with colorectal cancer obstruction and failure of stent insertion, (2) patients with colorectal cancer perforation requiring emergency surgery, (3) patients with T4 colorectal cancer lesion that could not be resected laparoscopically, and (4) patients with compromised cardio-pulmonary function in whom pneumoperitoneum under general anesthesia was contraindicated. In this study, transverse colon cancer was defined as lesions between the hepatic flexure and splenic flexure in the colon, requiring ligation of the middle colic vessels at their origin. CT or barium enema was performed in all patients with colon cancer preoperatively for localization of the tumor. If radiological localization was unclear, preoperative colonoscopic Indian ink tattooing or endoscopic clipping was performed. t χ 2 P Results Postoperative clinical outcomes 1 Table 1 Clinical characteristics of patients   N N P Age (years) 64.1 ± 11.3 62.5 ± 12.1 NS Sex (M:F) 15:19 46:48 NS 2 23.5 ± 3.0 24.0 ± 3.1 NS Operating time (min) a a NS Blood loss (ml) a a NS Time to pass flatus (days) 2.8 ± 0.8 2.6 ± 1.0 NS Diet start (days) 4.2 ± 1.8 4.2 ± 2.8 NS Hospital stay (days) 11.4 ± 4.1 11.2 ± 6.0 NS TCC OSCC NS a Oncological quality by pathologic outcomes 2 Table 2 Pathological outcomes of patients   N N P Tumor size (cm) a a NS PRM (cm) a a NS DRM (cm) a a NS No. of lymph nodes a a NS Radial margin (cm) a a NS TCC OSCC DRM PRM NS a Discussion 1 2 6 8 13 7 Transverse colon cancer occurs in about 10% of cases of colorectal cancer, and it often presents a challenge for the choice of the best surgical procedure based on the location of the tumor and extent of lymph node dissection. There could also be technical difficulties with laparoscopic identification, ligation, and lymph node dissection around the middle colic vessels depending on the surgeon’s experience. Because of these reasons, transverse colon cancer was excluded from almost every prior prospective randomized trial. Therefore, there is continued debate over the validity of laparoscopic surgery for transverse colon cancer. The major controversy about laparoscopic surgery for transverse colon cancer lies on whether or not it is feasible to perform sufficient extent of lymph node dissection around the middle colic artery laparoscopically. As experiences of laparoscopic surgery are accumulating and surgical techniques and instruments are developing, we consider that the extent of laparoscopic lymph node dissection for transverse colon cancer is not less than the extent of conventional lymph node dissection for transverse colon cancer. 14 15 16 17 18 19 20 There was one case of colon injury proximal to anastomosis caused by electrocautery during the operation in the OSCC group; this was treated by a laparoscopic simple closure on postoperative day 3. Three cases of anastomosis leak, one case of right hemicolectomy, and two cases of anterior resection occurred in the OSCC group. A patient with anastomosis leak was diagnosed by clinical symptoms or sign, fecal or purulent discharge from drain, fever, leukocytosis, and peritoneal irritation sign. Radiologic study using a water-soluble dye was not performed in this study. Of the three cases, one patient with a leak of anterior resection was treated conservatively successfully, and two patients with leak cases underwent laparoscopic re-operation. All other minor complications were successfully treated conservatively. Conversion to open surgery occurred in one case in the TCC group and in three cases in the OSCC group; these differences were not significant. Factors related to the tumor were the cause of conversion to open surgery. One case in the TCC group was converted to open surgery due to T4 lesion in the transverse colon cancer that invaded the anterior wall of the stomach. In the OSCC group, one case with a larger tumor that was hard to handle by laparoscopy, and two cases of sigmoid colon cancer that invaded the uterus were converted to open surgery. However, T4 colon cancer is not a contraindication for laparoscopy if en bloc resection could be performed with the laparoscopy. In those cases converted to open surgery, laparoscopic en bloc resection was impossible. This study has some weak points. First, the number of patients with transverse colon cancer is too small, making up 10% of the total colorectal cancer resection and 12% of the total laparoscopic colorectal resection in this study. The second is that although the data in this study were collected prospectively, the data were not derived from a larger case series and this study was not randomized controlled. The third is that the mean follow-up period was too short to evaluate the oncological outcomes (15.9 months; range 1–40 months). We think that large-scale prospective controlled trials and long-term analysis are mandatory to overcome these limitations and confirm the oncological safety of laparoscopic transverse colon cancer surgery. We are going to report a long-term analysis after a long-term follow-up involving more cases prospectively. Conclusions The results of this study show no significant differences with regard to surgical outcomes and oncological quality by pathologic outcomes between patients in the OSCC and TCC groups. Further investigations with large-scale prospective studies and long-term analysis of laparoscopic surgery for transverse colon cancer are mandatory to establish the oncological safety of laparoscopic surgery for transverse colon cancer.