Primary Neuroendocrine Carcinoma of the Appendix: A Case Report and Review of the Literature

Aim: We report on a rare case of appendiceal primary neuroendocrine carcinoma (NEC) and discuss three cases previously described. Case Report: A 58-year-old woman presented with acute abdominal pain and a low-grade fever. She was diagnosed with acute appendicitis and underwent laparoscopic appendectomy. Pathological examination of the resected specimen revealed NEC. Immunohistochemical analyses were positive for synaptophysin, chromogranin, and CD-56. The tumour was high grade and the Ki-67 index was >20%. Primary NEC of the appendix is extremely rare. To our knowledge, this is the first case report of an appendiceal NEC that meets the 2010 diagnostic criteria of the World Health Organization. Conclusion: Due to its non-specific clinical presentation, NEC is often misdiagnosed as appendicitis; however, it can advance rapidly and carries a very poor prognosis, despite chemotherapy. In the future, a treatment protocol for immunohistochemical analyses should be established to improve the survival rate. Neuroendocrine cells exist throughout the human body (1). Neuroendocrine tumours (NETs) are a heterogeneous group of neoplasms composed of cells containing dense-core neuroendocrine secretory granules in the cytoplasm (2). The World Health Organization (WHO) grouped high-grade NETs with neuroendocrine carcinoma (NEC) in the 2010 classification of the NETs (3). The gastrointestinal tract has the largest proportion of neuroendocrine cells (1), i.e. approximately two-thirds of NETs; one-quarter of these cells are present in the lungs and the remainder, in other endocrine