Metachronous Liver Metastasis during Long-term Followup after Endoscopic Submucosal Dissection of a Small Rectal Neuroendocrine Neoplasm

A 67-year-old woman underwent a screening colonoscopy, which revealed a 7-mm rectal subepithelial lesion. Endoscopic submucosal dissection (ESD) confirmed a grade 1 rectal neuroendocrine neoplasm (NEN), and no further treatment was administered. One year after ESD, she was diagnosed with lung cancer, which recurred 4 years later and required chemotherapy. Nine years after ESD, multiple liver metastases from the rectal NEN were found, which were well controlled with radiofrequency ablation. The patient died 13 years after ESD due to the progression of lung cancer. This case highlights the need for long-term follow-up in patients with small rectal NENs treated with endoscopic resection.