Indications for lateral lymph node dissection in patients with rectal neuroendocrine tumors: A case report and review of the literature.

The optimal surgical indications for small rectal neuroendocrine tumors (NETs) are controversial. Generally, treatment guidelines for rectal NETs >2 cm or with potential lymph node (LN) metastasis recommend formal oncologic low anterior resection (LAR) with total mesorectal excision (TME). However, rectal NETs have the potential to metastasize to the lateral lymph nodes (LLNs). To the best of our knowledge, there are no detailed reports in English on LLN metastasis from rectal NETs. A 47-year-old man diagnosed with a rectal NET underwent endoscopic submucosal dissection (ESD). The pathological diagnosis was NET G1. The tumor was 10 mm in diameter, and the tumor depth reached the submucosal layer. A period of 3 years after ESD, the patient was diagnosed with LN metastasis in the mesorectum and LLN metastasis on the left side from the NET. Robotic TME and bilateral LN dissection were performed. The pathological findings indicated that two of the 18 LNs in the mesorectum were metastatic, and all the LLNs on the left side were negative. In contrast, 1 of the 6 LLNs on the right side was metastatic. Early-stage rectal NETs can metastasize to the LLNs, and it is very difficult to detect LLN metastasis based on size alone. TME alone may be insufficient to treat rectal NETs, and additional LLN dissection may be an important treatment strategy. However, it is increasingly difficult to determine the surgical indications for optimally timed LLN dissection.