Prognostic significance of extranodal microscopic foci discontinuous with primary lesion in rectal cancer.

PURPOSE: The most common recurrence after curative resection of rectal carcinoma originates from tiny, undetectable residual foci within the pelvic cavity. The significance and methods used to predict the presence of extramural and extranodal microscopic cancer foci discontinuous with the main lesion of rectal cancers were investigated.
METHODS: Four hundred twenty-seven patients who underwent resection of rectal carcinoma were studied. All resected specimens were examined for histologic evidence of extramural cancer separate from the main lesion.
RESULTS: Extramural cancers not in continuity with the main rectal lesion were classified as follows: 1) extranodal microscopic cancers; 2) large tumor nodules; 3) lymph node metastases. Each classification was found to influence long-term prognosis. Among them, microscopic cancer was thought to be especially relevant because, by virtue of its microscopic nature, it may be left in the pelvic cavity, causing local recurrence. The existence of large tumor nodules and metastatic lymph nodes correlated closely with the presence of microscopic cancer. Because large tumor nodules and lymph node metastases are possibly detectable during the operation by palpation and may be analyzed by microscopic frozen sections, they might be useful predictors of the presence of microscopic cancers.
CONCLUSIONS: In cases with extensive local rectal cancer spread, the nerve-sparing rectal resection that omits lateral dissection may be insufficient for local control because of incomplete removal of occult microscopic cancer, resulting in local recurrence. Presence of microscopic cancer correlates closely with large tumor nodules and metastatic lymph nodes. Intraoperative frozen section investigations may, thus, help in deciding on extent of location resection.