Anatomical-specific Lymphatic Route Beyond Mesorectal Fascia: Analyses from Female Cadavers and Patients With Rectal...

This study aimed to clarify the lymphatic network around the anorectum using cadavers and consider a treatment strategy for locally advanced lower rectal cancer (LARC).

We performed microscopic observations of three female cadavers using India ink into the submucosa at the dentate line (DL) of the cadaver. We examined the clinical outcomes of 74 patients with LARC who underwent total mesorectal excision after preoperative treatment, classifying them as anterior (A), lateral (L), or posterior (P) based on the deepest part of the tumor.

Two of the three anterior walls contained the Denonvilliers' fascia (DVF), and the DVF became indistinct at the height of DL, where India ink extended to the vagina via the perivascular space and was absorbed into the vaginal lymph vessels. One case did not have DVF, and lymph vessels in the rectum distributed in close proximity to vagina. On the lateral posterior wall, the ink spread extensively from DL and the front of the levator ani muscle, whereas on the posterior wall, lymph vessels containing absorbed ink were observed from the hiatal ligament to the front of the sacrum. In the survival analysis, the 3-year disease-free survival rates were 71.9%, 100%, and 69.7% for A, L, and P groups, respectively, with a higher recurrence rate in the anterior and posterior walls.

Lymphatic network beyond fascia around anorectum was spread to a specific route by location. The anatomical diversity of this network was thought to be involved in the poor outcome for LARC.