Distal intramural spread of carcinoma of the rectum correlated with lymph nodal involvement.

One hundred and nineteen operative specimens of carcinoma of the rectum were prospectively studied to evaluate distant microscopic intramural spread with respect to gross tumoral margins and to determine if the degree of spread was related to involvement of the lymph nodes. Eighty-eight of the 119 specimens (74 per cent) did not have intramural extension distal to the gross distal margin of the tumor. Twenty-five (21 per cent) had intramural extension of less than 5 millimeters from the gross distal limit of the tumor. In these instances, tumoral spread was contiguous. In six (5 per cent), tumoral spread was found at more than 5 millimeters from the gross distal margin of the lesion. In all six specimens, the tumoral extension was separated from the gross lesion by undiseased tissue, the foci being located between 5 and 15 millimeters from the distal margin of the lesion. Lymph nodal involvement was found in 19 of 88 lesions without distal intramural spread, in 14 of 25 tumors with intramural spread of less than 5 millimeters and in five of six with intramural extension of 5 millimeters or more, respectively. The difference was statistically significant. With respect to the same three categories of distal extension, more than one lymph node was involved in 11 of 88 lesions, six of 25 and five of six, respectively. This difference was also statistically significant. In the six instances with distal intramural extension, results of immunohistochemical staining demonstrated the presence of tumoral embolism in both the blood and lymphatic vessels. In carcinoma of the rectum, lymph nodal involvement and its multiplicity are directly related to the extent of intramural spread.