Gastric mixed neuroendocrine/non neuroendocrine neoplasia: a rare entity

Gastric neoplasms have different histological subtypes. Mixed neuroendocrine/non neuroendocrine neoplasms (MiNEN), as defined by the World Health Organization (WHO) 2019 Classification of Tumours of the Digestive System, are rare composite tumours bearing morphological characteristics of more than one histological type. Historically, the diagnosis requires that each component accounts for at least 30% of the total tumour burden. We present the case of a 70-year-old male, who was referred to our endoscopy unit for resection of a depressed lesion (Paris classification type 0 IIc) of 40mm in largest diameter, located on the lesser curvature of the gastric body. The lesion was submitted to en bloc resection by endoscopic submucosal dissection. Histological examination revealed a poorly differentiated intramucosal adenocarcinoma and a grade G3 well differentiated neuroendocrine tumour (NET), on a background of chronic atrophic gastritis. Unfortunately, examination of the NET component revealed intercepted margins. The patient is currently undergoing tumour staging and will be discussed by a multidisciplinary team to determine subsequent management.