Neuroendocrine tumors (NET) are relatively uncommon rectal neoplasms, and the liver is the most common site of distant metastasis. Simultaneous liver and colorectal resections by minimally invasive surgery and natural orifice specimen extraction are gaining popularity, reducing morbidity. We describe a case of rectal NET with liver metastasis operated simultaneously by laparoscopy with both specimens extracted via the anal canal. Transanal or transvaginal natural orifice specimen extraction surgery for suitable cases is underutilized and only isolated case reports for simultaneous resections exist.

The 2019 revised World Health Organization (WHO) classification of tumors of endocrine organs classifies grade 3 gastroenteropancreatic neuroendocrine neoplasms (GEP-NEN G3) into well-differentiated tumors (NET G3) and poorly differentiated carcinomas (NEC G3). There are few reported cases of NET G3 occurring in the rectum. A 71-year-old man complained of bright red blood in his stool. Total colonoscopy revealed a mass in the lower rectum. Pathologic examination yielded a diagnosis of group 1. Computed tomography revealed swollen paraintestinal lymph nodes and multiple liver metastases. We performed laparoscopic abdominoperineal resection not only to avoid the unbearable symptoms caused by tumor growth but to make a pathological diagnosis. The tumor measured 3.5 × 2.8 cm, and the pathological diagnosis was stage IV neuroendocrine carcinoma. He underwent chemotherapy with irinotecan plus cisplatin, followed by carboplatin plus etopside, but his disease did not respond to either regimen. Twenty-seven months after surgery, he died of his disease. Upon re-examination of the surgical specimen, the tumor was consistent with the 2019 WHO classification of NET G3.6 CONCLUSION: A definite diagnosis of NET G3 or NEC G3 must be made to determine the appropriate treatment strategy for patients with GEP-NEN G3. Further case reports and case series are needed to establish the optimal therapy.

An 81-year-old man with Cushing syndrome was referred for a Ga-DOTATATE PET/CT study to investigate for an ectopic source of adrenocorticotropic hormone. The scan demonstrated mildly increased octreopeptide uptake at a rectal mass and focal uptake at multiple regions throughout the bone marrow of the axial skeleton, consistent with metastases. A subsequent F-FDG PET/CT study was performed for further evaluation and demonstrated markedly increased metabolism at the previously identified rectal mass, in addition to the liver and multiple regions throughout the skeleton. Histopathology from biopsy of the rectal mass confirmed a small cell neuroendocrine carcinoma.