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[Outcome of total mesorectal excision for lower rectal cancer: micrometastasis in the mesorectum].

OBJECTIVE
To assess the correlation between micrometastasis in mesorectum and pathological factors after total mesorectal excision(TME) in lower rectal cancer.


METHODS
All lymph nodes were obtained by fat clearance from 31 lower rectal cancer patients with TME. The lymph nodes which had previously been considered negative of metastasis by conventional examination were submitted to immunohistochemical examination to identify the micrometastases using anti-cytokeratin antibody. The correlation between micrometastasis and pathological factors were analyzed.


RESULTS
One thousand and seven LNs were collected from 31 patients. One hundred and five LNs were found positive by conventional examination, and the mean diameter was (5.5 +/- 3.1) mm. The mean diameter of conventional negative LNS was (2.8 +/- 1.5) mm. The diameter differed significantly between conventional positive and negative LNS (P < 0.05). In 902 conventional negative LNs, 26 contained micrometastasis (209%) and the mean diameter was (3.3 +/- 1.2) mm. The diameter of LNs with micrometastasis was significantly smaller than that of conventional positive LNs (P < 0.05). The diameter of most of the micrometastatic LNs(88.5%) was less than 5 mm. Fourteen patients (38.7%) contained micrometastasis. The pathological stage, serum carcinoembryonic antigen level and tumor differentiation were related to micrometastasis (P < 0.05).


CONCLUSIONS
With the detection of micrometastasis after fat clearance, we can estimate the LN metastasis status more accurately. It can be useful in clinical staging and individual treatment of rectal cancer.