Clinicopathological study of intrapelvic cancer spread to the iliac area in lower rectal adenocarcinoma by serial sectioning

Background: The role of iliac lymphadenectomy in surgery for rectal cancer remains unknown. Detailed clinicopathological data on lateral cancer extension may be needed to determine the true role of this procedure. Methods: Seventy consecutive patients with low rectal cancer who underwent systematic iliac lymphadenectomy between 1991 and 1995 were reviewed. The iliac area was divided into five regions: (1) middle rectal root, (2) internal iliac, (3) obturator, (4) common iliac and (5) external iliac. Iliac lymph nodes that were cancer-free based on conventional pathological examination were serially sectioned at 100-mu m intervals and re-examined for occult microscopic involvement. Results: Occult microscopic foci were detected in five (7 per cent) of the 70 patients, and the overall incidence of lateral cancer spread was 24 per cent (17 of 70). Among patients without other sites of distant metastasis or circumferential involvement of the margin, the 5-year survival rate of those with lateral spread was 35 per cent. Although the prognosis of patients with cancer involving multiple iliac regions was poor, three of six patients with metastasis to only a single region were alive without disease at 3 years. Conclusion: Surgeons should be aware of the possibility of localized lateral spread, including microscopic metastasis, when determining the optimum procedure for iliac lymphadenectomy in patients with rectal cancer.