Lymphovascular and neural invasion in low-lying rectal carcinoma.

We have previously demonstrated that lymphovascular infiltration was correlated with an increased risk for developing lymph node metastasis in rectal adenocarcinomas confined within the submucosal layer. In another study, lymphovascular infiltration was also correlated with poor prognosis for patients with advanced rectal cancers. Considerations that low rectal tumors have an increased risk to develop recurrence and neural invasion have been recently implicated with a more localized pattern of tumor spread. We therefore assessed the lymphovascular and neural invasion in 65 specimens from patients with low rectal cancers who underwent curative operation to determine its implications in the treatment and prognosis. Lymphovascular invasion was noted in 60%, and neural invasion was found in 27% of the cases. Five-year survival rates (Kaplan-Meier method) were significantly decreased in patients with lymphovascular invasion (31 vs. 67%; p < 0.01) or neural invasion (30 vs. 58%; p < 0.01). Neither lymphovascular nor neural invasion was noted in Dukes' stage A tumors. There was no recurrence or distant metastasis in these patients. However, lymphovascular and neural invasion increased with tumor stage. Local recurrence and distant metastasis occurred respectively in three and four, and five and five patients with Dukes' B and C tumors, respectively. Both Dukes' B and C cases with local recurrence had a higher incidence of neural invasion as compared with the disease-free group. These results suggest that postoperative assessment of venous and neural invasion may provide valuable information to better determine which patients with low rectal cancers would benefit from adjuvant treatment.