Histopathological characteristics of lateral lymph nodes dictate local or distant metastasis and prognosis in low rectal cancer patients

Objectives: The therapeutic value of lateral lymph node dissection in low rectal cancer (RC) patients remains a matter of debate. The present study evaluated the dissection value of each lateral lymph node, based on its histopathological characteristics. Methods: This study enrolled 381 consecutive RC patients with bilateral lateral lymph node dissection, from 1995 to 2014. We investigated their clinicopathological characteristics, and the therapeutic value of each lymph node dissection. The therapeutic values of the distal internal iliac and obturator lymph nodes were further investigated on the basis of histopathological classifications, as follows: minimum metastasis (Type A), massive metastasis (Type B) without capsular invasion, and invasive metastasis (Type C) with capsular invasion and were evaluated by the local or distant recurrence and 5 year overall survival. Results: Among the lateral lymph nodes, the therapeutic values of distal internal iliac (6.1) and obturator (7.4) lymph node dissection were higher than those of common (0.4) and proximal iliac (1.2) lymph node dissection. However, our further investigation revealed that the 5 year overall survival rates of Type C (obturator/distal iliac) were 12.5%/22.9%, whereas those of Type A and Type B were 100%/91.6% and 77.8%/50.0%, respectively. Conclusions: Metastasis and prognosis of RC patients depend on the histopathological characteristics of the distal internal iliac and obturator lymph nodes. The present study provides new insights for choices of appropriate treatments for RC patients.