Most gastric neuroendocrine tumours are well differentiated and considered as neuroendocrine neoplasms, whilst poorly differentiated lesions are considered as neuroendocrine carcinomas and account for only 6-16% of gastric neuroendocrine tumours. Gastric mixed adenoneuroendocrine carcinomas are rare malignancies usually composed of a neuroendocrine carcinoma and an adenocarcinoma with a variable grade of differentiation. Here, we report an unusual and rare gastric mixed adenoneuroendocrine carcinoma with a trilineage cell differentiation including a neuroendocrine carcinoma, an adenocarcinoma and a squamous cell carcinoma. A brief discussion of the histopathological features, biological behaviour and treatment of this rare tumour type is presented.
Keywords: Gastric neuroendocrine tumours; MANEC; Trilineage differentiation.