Objective: To investigate the influence of lymph nodes detection on the pathological staging in rectal cancer specimens.
Methods: From January 2007 to June 2008, 75 patients with rectal cancer who underwent total mesorectal excision were randomly divided into two groups: conventional group (n = 39), in which lymph nodes were detected by sight and palpation; fat clearance group (n = 36), in which lymph nodes were harvested after the specimens immersed in a fat clearance solution for 24 hours. The lymph node number harvested was compared between the two groups, and metastasis of the lymph nodes and its impact on the pathologic staging was analyzed in the two groups.
Results: A total of 75 patients (42 male and 33 female, the average age was 53.2 years) were enrolled in this study. In the conventional group, a mean of 14.4 lymph nodes (range, 8 - 27) was detected, and was significantly less than that in fat clearance group (mean 36.2, range, 18 - 62) (t = 5.800, P < 0.05). The tumor invasion was classified as T1 in 4 cases and 5 cases, T2 in 9 cases and 6 cases, T3 in 24 cases and 22 cases and T4 in 2 cases and 3 cases in conventional group and fat clearance group, respectively. No significant difference was found in T classification between the two groups (Z = 0.160, P = 0.850). The mean number of metastatic lymph nodes harvested in conventional group was 1.5, and it was 3.2 in the fat clearance group (Z = 3.500, P < 0.05). According to the regional lymph nodes, patients classified as N0, N1 and N2 were 20, 12, 7 cases in conventional group, and were 9, 14, 13 cases in the fat clearance group, respectively; and there was significant difference between the two groups (Z = 2.410, P = 0.016).
Conclusions: The variation of the number of harvested lymph nodes in surgical specimens from rectal cancer after total mesorectal excision is great. The metastasis of mesorectal lymph nodes is not only associated with the tumor staging, but also related to the number of harvested lymph nodes. It is questionable that 12 lymph nodes is currently seen as enough to evaluate the pathologic staging for rectal cancer.