Distribution and patterns of lymph nodes metastases and micrometastases in the mesorectum of rectal cancer

Abstract

Background and Objectives Facts buried in the mesorectum remain to be unveiled. This study investigated the number, size, and detailed distribution of lymph nodes metastases and micrometastases within the mesorectum of rectal cancer. Methods Thirty-one patients who underwent total mesorectal excision (TME) were treated with lymph node revealing solution to retrieve lymph nodes, which were submitted to hematoxylin and eosin (HE) examination and immunohistochemical (IHC) staining. Results The mean number of mesorectal nodes per case was 17.7. The mean size of metastatic, micrometastatic, and isolated tumor cells (ITC) harbored nodes was 5.2 mm, 4.5 mm, and 3.3 mm, respectively. Most of the metastatic (92.1%), micrometastatic and ITC-involved nodes (69.2%) were located along the superior rectal artery (SRA). Posterior-wall located tumor might spread along both sides of the mesorectum simultaneously (P = 0.34), while lateral-wall located tumor spread preferably to ipsolateral side versus contralateral side (P = 0.012). Conclusion Most of the metastases and micrometastases positive lymph nodes were smaller than 5 mm and distributed along the SRA. The patterns of lymph nodes spread were related to the circumferential situation of tumor in the rectal wall. Surgical excision of the rectal cancer should completely remove the whole mesorectum, especially to avoid any damage of the mesorectum on tumor side. J. Surg. Oncol. 2007;96: 213–219.