AIM:To investigate the number,size,and status of lymph nodes within the mesorectum and to explore the prognostic significance of lymph node micrometastases in patients with rectal cancer. METHODS:Thirty-one patients with rectal cancer undergone total mesorectal excision between October 2001 and October 2002 were included.Mesorectal nodes retrieved from the resected specimens were detected with a combination of haematoxylin and eosin(HE)staining and immunohistoch- emistry(IHC).The relations between lymph node metastases, micrometastases and postoperative recurrence were analyzed. RESULTS:A total of 548 lymph nodes were harvested, with 17.7±8.2 nodes per case.The average number of metastatic nodes in HE-positive patients and micrometastatic nodes in IHC-positive patients was 5.2±5.1 per case and 2.2±1.3 per case,respectively.The mean size of all nodes and metastatic nodes was 4.1±1.8 mm and 5.2±1.7 mm in diameter,respectively.The mean size of micrometastatic nodes was 3.9±1.4 mm in diameter.The size of the majority of mesorectal nodes(66.8%),metastatic nodes(52.6%),and micrometastatic nodes(79.5%)was less than 5 mm in diameter. During a median follow-up period of 24.6±4.7 too,5 patients (16.7%)had recurrence,of them 2 died and 3 survived. Another case died of tumor unrelated cause and was excluded. All 5 recurrent cases had 3 or more nodes involved,and one of them developed only lymph node micrometastases.The mean number of both metastatic and micrometastatic nodes per case differed significantly between the recurrent and non-recurrent groups(P<0.01 and P=0.01,respectively). CONCLUSION:The majority of lymph nodes,metastatic, and micrometastatic lymph nodes within the mesorectum are smaller than 5 mm in diameter.The nodal status and the number of lymph nodes involved with tumor metastases and micrometastases are related to the rapid postoperative recurrence. A investigate the number, size, and status of lymph nodes within the mesorectum and to explore the prognostic significance of lymph node micrometastases in patients with rectal cancer. METHODS: Thirty-one patients with rectal cancer undergone total mesorectal excision between October 2001 and October 2002 were included. Mesorectal nodes retrieved from the resected specimens were detected with a combination of haematoxylin and eosin (HE) staining and immunohistoch- emistry (IHC). The relations between lymph node metastases, micrometastases and postoperative recurrence were analyzed. RESULTS: A total of 548 lymph nodes were harvested with 17.7 ± 8.2 nodes per case. The average number of metastatic nodes in HE-positive patients and micrometastatic nodes in IHC-positive patients was 5.2 ± 5.1 per case and 2.2 ± 1.3 per case, respectively. The mean size of all nodes and metastatic nodes was 4.1 ± 1.8 mm and 5.2 ± 1.7 mm in diameter, respectively. The mean size of micrometastatic nodes was 3.9 ± 1.4 mm in diameter of the majority of mesorectal nodes (66.8%), metastatic nodes (52.6%), and micrometastatic nodes (79.5%) were less than 5 mm in diameter. During a median follow-up period of 24.6 ± 4.7 too, 5 patients (16.7%) had recurrence, of them 2 died and 3 survived. Another case of of unreserved cause and was excluded. All 5 recurrent cases had 3 or more nodes involved, and one of them published only lymph node micrometastases.The mean number of both metastatic and micrometastatic nodes per case differed significantly between the recurrent and non-recurrent groups (P <0.01 and P = 0.01, respectively). CONCLUSION: The majority of lymph nodes, metastatic, and micrometastatic lymph nodes within the mesorectum are smaller than 5 mm in diameter. The nodal status and the number of lymph nodes involved with tumor metastases and micrometastases are related to the rapid postoperative recurrence.