Lymphatic spread and its prognostic value in patients with rectal cancer.

The incidence of lymph node metastasis in 423 patients with resected rectal cancer was 51.4 percent. There was no correlation between the size of the tumor and metastasis when the maximum diameter of the tumor exceeded 3 cm, and metastasis was seen in more than 50 percent of the patients. Metastasis was seen in 17.9 percent of the patients with cancer limited to the mucosa (mucosal and submucosal layer), in 37.8 of those with penetration limited to the propria muscle, and in more than 50 percent of those with penetration to the serosa or invasion into other organs. With lower rectal cancer, lateral metastasis was seen in 23 percent of the patients with advanced cancer, and inguinal lymph node metastasis in 6 percent. The 5 year survival rate of Dukes' C patients was as low as 33 percent, but was 52.9 percent in the patients with metastasis to only the pararectal lymph node; the prognosis of lateral metastasis is poor. As a subclassification of Dukes' C, levels 1, 2, 3, 4, and 5 are proposed on the basis of the extent of lymphatic spread.