[Rectal neuroendocrine tumors of the rectum: update on endoscopic and surgical treatment]

Rectal neuroendocrine tumors (rNET) are rare but increasingly more common entities, which are usually an incidental finding during routine colonoscopy. The rNETs are usually well-differentiated with low metastatic potential. Thus, staging is only required in high-risk situations (size ≥ 10 mm, invasion of the muscularis propria, grading > G1, L1, V1). Endoscopic resection is the most frequently used treatment. Based on the depth of invasion, endoscopic mucosal resection (EMR), endoscopic submucosal dissection (ESD) or endoscopic full-thickness resection (EFTR) are applied. In cases of R1 resection, re-endoscopic resection can be conducted to achieve R0 status. Radical surgical resection with higher or lower anterior rectum (HAR/LAR) resection with total mesorectal excision (TME) is indicated for rNETs > 20 mm, rNETs between 10-20 mm with risk factors (R1 resection after second endoscopic resection, Ki67 > 10%, L1, V1), lymph node metastasis and also in cases of distant metastasis if those are also resectable. In cases of unresectable distant metastasis, systemic treatment is applied. The prognosis after treatment of well-differentiated rNETs is generally favorable.