The purpose of this study is to investigate the metastatic status of lateral pelvic lymph nodes in rectal neuroendocrine neoplasms (rNENs) undergoing laparoscopic total mesenteric excision (TME). The hypothesis is that the rate of lateral lymph node metastasis is underestimated in rNENs undergoing TME, necessitating concurrent lateral Pelvic lymph node dissection.

This study is a prospective single-arm clinical study. 30 patients with rNENs undergoing TME are planned to be included in the study. The purpose of this study is to investigate the metastatic status of lateral pelvic lymph nodes in (rNENs) undergoing laparoscopic TME. The primary endpoint is the rate of lateral pelvic lymph nodes metastasis. The primary hypothesis was the rate of lateral lymph node metastasis is underestimated in rNENs undergoing TME, necessitating concurrent lateral Pelvic lymph node dissection.

This study seeks to report for the first time the true status of lateral pelvic lymph node metastasis in these patients. In addition, the proportion of patients with radical resection (R0), surgical complication profile, and quality of life (QoL) are also secondary endpoints.

Inclusion Criteria:

1. Biopsy proven rectal neuroendocrine neoplasm (neuroendocrine tumor and carcinoma);

2. Meets any one of the following conditions:

   • Preoperative imaging examinations reveal that the maximum diameter of the tumor is greater than 2cm.
   • Preoperative imaging examinations reveal that the maximum diameter of the tumor is between 1-2cm and the clinical staging is T2 or higher.
   • Preoperative imaging examinations reveal that the maximum diameter of the tumor is between 1-2cm and is categorized as Grade 3 differentiation.
   • Recurrence after local excision under endoscopy.

3. Eastern Cooperative Oncology Group(ECOG) performance score ≤ 1;

4. Written informed consent;

Exclusion Criteria:

1. Complete intestinal obstruction;
2. Hepatitis activity and peripheral neuropathy (such as peripheral neuritis, pseudo meningitis, motor neuritis, and sensory impairment);
3. Significant organ dysfunction or other significant diseases, including clinically relevant coronary artery disease, cardiovascular disease, or myocardial infarction within the 12 months before enrollment; severe neurological or psychiatric history; severe infection; active disseminated intravascular coagulation；
4. Pregnancy or breastfeeding;
5. Alcohol abuse or drug addiction;
6. Concurrent uncontrolled medical condition;

Participants' data are only allowed to be used for the analysis of this study and are not authorized to be shared with other researchers.