Proposed distal margin for resection of rectal cancer.

To determine the adequate distal margin, particularly from the point of extent of lymph node metastasis, 2,333 lymph nodes from 44 patients with rectal carcinoma were evaluated, using a clearing method. The tumors were divided into two growth patterns; infiltrative and localized. Lymph node metastasis was histo-pathologically examined with special attention focused on nodes on the distal side of the tumor. The intramural spread was also given attention. The proximal pararectal lymph nodes often contained malignant cells, whereas the distal ones were rarely involved, and if involved, they were present within 1 cm from the tumor. Pararectal lymph node metastasis and intramural spread were seen with a range of 1 cm and 0.5 cm, respectively, in the localized type and 1 cm and 2.1 cm, respectively in the infiltrative type. Based on these findings, the distal margin for surgical resection of rectal carcinoma is considered to be 2 cm for the localized type and 3 cm for the infiltrative type.