[A Case of Early Rectal Cancer Mixed NET G3 and Recurrent Liver Metastasis Shortly after Surgery].

We report a case of early rectal cancer mixed neuroendocrine tumor Grade 3(NET G3)that rapidly metastasized. A 76- year-old woman was diagnosed with a rectal tumor in the lower rectum and underwent endoscopic submucosal dissection. Pathology showed tub2>por2, pT1b(2,700μm)with NET G3 features in less than 30% of the lesion. Immunohistochemistry was positive for synaptophysin and chromogranin A, negative for CD56. Despite abdominoperineal resection with D3 dissection, a large liver metastasis appeared 6 months after surgery. Liver biopsy confirmed similarity to the rectal NET G3 component. The patient died 13 months postoperatively despite chemotherapy. This case highlights that even small NET G3 components in early rectal cancer may indicate poor prognosis.