[Is it possible to predict lateral lymph node metastasis by their sizes in patients with lower rectal cancer?--analysis of paraffin-embedded sections].

Considering the advantages and disadvantages of lateral lymph node dissection in patients with lower rectal cancer, it would be ideal to select candidates for lateral lymph node dissection by preoperative imaging study. This preliminary study was performed to examine whether it would be possible to predict lateral lymph node metastasis by their sizes in patients with lower rectal cancer. In study-1, we measured the maximal and minimal diameter of 17 lateral lymph nodes from 2 patients on the paraffin-embedded slides and compared them to the diameters of the fresh specimen. In study-2, a relationship between the size of lateral lymph nodes and the presence of metastasis was examined in 259 lateral lymph nodes from 35 patients. The mean reduction rate after paraffin embedding was 56.8% (34.7-78.8) for the maximal diameter and 62.0% (36.7-80.5) for the minimal diameter. The maximal (p<0.01) and minimal diameters (p<0.01) were significantly greater in the nodes positive for metastasis than in the negative nodes. The area under the receiver operating curve was significantly greater for the minimal diameter than for the maximal diameter( p=0.07). The sensitivity, specificity, and accuracy for predicting metastasis was 78.6%, 83.7%, and 83.4%, respectively when the cut off of the minimal diameter was set at 3.41 mm, which corresponds to 5.50 mm in living bodies. In conclusion, determining the minimal diameter of the lateral lymph nodes by preoperative imaging studies may be useful for selecting candidates for lateral lymph nodes dissection.