An unexpected case of large cell neuroendocrine carcinoma of the colon: a case report.

Background: Patients presenting with large cell neuroendocrine carcinomas (LCNECs) comprise a small minority of total colon and rectal cancers (1-2%) with poor prognostic outcomes in lieu of late diagnosis and metastasis at the point of diagnosis. Case Description: We report a case presentation of a 69-year-old male presenting with diffuse, non-severe upper abdominal pain and a positive at-home colon cancer screening test. At the time of presentation, the patient was negative for constipation or blood in stool. The patient underwent a colonoscopy with biopsy results positive for LCNEC within the proximal ascending colon. A right hemicolectomy was performed with subsequent pathology indicating a poorly differentiated LCNEC with 4/18 positive nodes and final pathology showing stage IIIA (T3, N1, M0) with Ki-67 index at 70%. Post-operative intervention included two cycles of carboplatin and etoposide as well as routine follow-up for labs, imaging, and pharmacological management. Conclusions: LCNECs are highly aggressive with poor prognostic outcomes and high mortality rates on both 1- and 5-year survival scales. Prior studies and reports indicated a need for further research and data investigating treatment standardization for patients diagnosed with LCNECs. In lieu of this, this study provides a potential standardized treatment modality combining both European Neuroendocrine Tumor Society (ENETS) and North American Neuroendocrine Tumor Society (NANETS) consensus guidelines.