Lymph Node Size Alone Is Not an Accurate Predictor of Metastases in Rectal Cancer: A Node-for-Node Comparative Study of Specimens and Histology

Although size criteria have been proposed to identify lymph node metastases in patients with rectal cancer, size may not be an accurate predictor. Specimens from consecutive rectal cancer patients who underwent curative-intent radical surgery were examined. The long and short axes of lymph nodes were measured on the glass slides using micrometer calipers. The pathologic diagnosis was used as the reference. The diagnostic accuracy of metastatic status according to lymph node size was evaluated. Overall, 1283 lymph nodes from 78 patients were reviewed. The metastatic rate correlates with the length of both the long and short axes. However, metastases were present even in 1-mm lymph nodes, and the metastatic rate exceeds 5 per cent in lymph nodes measuring 3 mm along both axes. Cutoff values of ≥4 mm and ≥3 mm for the long and short axes result in a sensitivity of 76 per cent and 79 per cent, and a specificity of 36 per cent and 33 per cent, respectively, for each axis. Size criteria alone do not accurately predict the N-stage of rectal cancer. Diminutive lymph nodes, which are not seen on imaging studies, can contain metastatic disease.