Extra-Appendiceal Neuroendocrine Expressing Goblet Cell Adenocarcinoma of the Cecum—A Case Report and Brief Review of the Literature

<b>Background and Clinical Significance</b>: Neuroendocrine expressing goblet cell adenocarcinomas (GCAs) are uncommon clinically aggressive tumours of the digestive system, originating almost exclusively in the ileocecal appendix. GCA's singularity comes from its amphicrine nature, expressing both neuroendocrine and exocrine characteristics. The case report's objective is to raise awareness of this neoplasia's possible extra-appendiceal localisation by showcasing a GCA involving the cecum with no detectable appendiceal tumour. <b>Case Presentation</b>: The authors present a case of GCA with neuroendocrine expression in an 82-year-old male patient with severe anaemia and comorbidities who underwent a right colectomy and had no histopathological evidence of appendiceal tumour involvement. Immunohistochemical testing was performed using synaptophysin, chromogranin A, neuronal specific enolase, CD56, CDX-2, CK20, CEA, MUC2 and Ki67, thus establishing the final diagnosis of high-grade extra-appendiceal goblet-cell adenocarcinoma of the cecum, G3. The patient died on postoperative day 26 due to pneumonia and acute renal failure in a chronic renal disease context. <b>Conclusions</b>: Extremely few cases of extra-appendiceal GCA have been reported. Appendiceal evaluation with the exclusion of this possible origin should be mandatory in such cases for a correct classification. These tumours do not benefit from any official management protocols concerning clinical evaluation, and their treatment is commonly based on the tumour's stage, as in classical adenocarcinoma.