OBJECTIVETo investigate the pattern of lymph node metastasis in patients with left-sided colon cancer in order to provide evidences for the choice of operation mode and the range of lymph node clearance.

METHODSClinical data of 556 cases with left-sided colon carcinoma undergoing surgical treatment in Department of Colorectal Surgery, Fujian Medical University Union Hospital from January 2000 to October 2014 were retrospectively analyzed. Among these patients, cancer of splenic flexure and transverse colon close to splenic flexure (splenic flexure group) was found in 41 cases, descending colon cancer in 73 cases(descending colon goup) and sigmoid colon cancer in 442 cases (sigmoid colon group), respectively; T1 was found in 29 cases, T2 in 63 cases, T3 in 273 cases, T4 in 191 cases. All the patients underwent D3 radical operation or complete mesocolic excision(CME). Para-bowel lymph node was defined as the first station, mesenteric lymph node as the second station, and lymph node in root of mesentery and around upper and inferior mesenteric arteries as the third station. Metastasis was compared among these 3 stations with regard to different sites and tumor invasions.

RESULTSThe total lymph node metastasis rate was 49.6%(276/556). The lymph node metastasis rates of splenic flexure, descending colon and sigmoid colon groups were 53.7%(22/41), 52.1%(38/73) and 48.9%(216/442) respectively without significant difference (P>0.05). The lymph node metastasis rates of the first, second, and third stations were 47.3%(263/556), 16.9%(94/556) and 5.8%(32/556) respectively with significant difference (χ(2)=287.54, P=0.000). In the first, second and third station, the lymph node metastasis rate was 13.8%(4/29), 0 and 0 in T1; 25.4%(16/63), 4.8%(3/63) and 3.2%(2/63) in T2; 45.8%(125/273), 14.7%(40/273) and 4.8%(13/273) in T3; 61.8%(118/191), 26.7%(25/191) and 8.9%(17/191) in T4 respectively. In splenic flexure group, metastasis rates were similar between No.222 and No.232[14.6%(61/41) vs. 12.2%(5/41), χ(2)=0.11, P=1.000] and between No.223 and No.253 [7.3% (3/41) vs. 2.4% (1/41), χ(2)=1.05, P=0.616]. In descending colon group, metastasis rate of No.232 was higher as compared to No.222[15.1%(11/73) vs. 2.7% (2/73), χ(2)=6.84, P=0.017]; metastasis rate of No.253 was slightly higher as compared to No.223 without significant difference [4.1%(3/73) vs. 0, χ(2)=3.06, P=0.245]. Metastasis rates of No.222 and No.223 in splenic flexure group were significantly higher than those in descending colon and sigmoid colon groups (χ(2)=5.69, P=0.025; Fisher exact test, P=0.044); While such rates of No.232(No.242 for sigmoid colon group) and No.253 were not significantly different among 3 groups respectively (χ(2)=0.90, P=0.660; χ(2)=1.14, P=0.611).

CONCLUSIONSLeft-sided colon cancers in T1 should undergo D2 radical operation, while cancers in T2 to T4 should undergo D3 radical operation. The D3 radical operation for splenic flexure cancers and cancers of transverse colon close to splenic flexure should clear No.223 and No.253. The D3 radical operation for descending colon cancer should clear No.222 and No.253. The D3 radical operation for sigmoid colon should clear No.253.