A Case of Fifteen Simultaneous Rectal Neuroendocrine Tumors and Endocrine Cell Micronests Resected by Both Endoscopic Treatments and Surgery

CASE REPORT: A 65-year-old man without any symptoms received colonoscopy for cancer screening and underwent cold snare polypectomy (CSP) for a 3-mm rectal lesion at a local clinic. A histopathological examination revealed neuroendocrine tumor (NET) G1 with a positive margin. The patient was referred to our hospital for further treatment. Then, the post-CSP scar was removed by endoscopic submucosal dissection (ESD), with a sufficient endoscopically normal margin. Histopathology showed 4 NETs and endocrine cell micronests (ECMs) distant from the post-CSP scar, with a positive lateral margin. We considered that the possibility of other NETs was high. Additional surgery was performed. After a histopathological examination, 11 NETs and ECMs were found in the whole rectum, without lymph node metastasis. The patient had no recurrence at 24 months after surgery. In the past 10 years, we have experienced 4 cases (including the present case) of multiple rectal NETs among 56 cases of rectal NETs of ≤10 mm (7.1%). None of our 4 cases showed any recurrence (follow-up period: 12–32 months). CONCLUSIONS: We herein report a case involving a patient with 15 rectal NETs and ECMs. We reviewed our experience with multiple rectal NETs, and the rate of multiple rectal NETs was 7.1%. Endoscopists should consider that multiple lesions may be present in cases of rectal NET and be aware that some cannot be detected endoscopically.