LAUSR

Mixed neuroendocrine – non-neuroendocrine neoplasm (MiNEN) was a term initially applied to tumors arising in the pancreas. The concept was subsequently applied to extrapancreatic tumors with similar char-acteristics. MiNENs are generally composed of both adenocarcinoma and neuroendocrine carcinoma components, each representing at least 30% of the tumor, according to the current World Health Organization guidelines. 1 MiNENs of the intestine frequently originate from the colorectum, but rarely from the small bowel. 2 MiNENs can be divided into well-differentiated and poorly differentiated tumors. The pathogenesis of MiNEN remains unclear. A MiNEN is considered a neoplasia originating from pluripotent stem cells through an oncogenic process with posterior bidirectional differentiation. 3 However, the tumor components can appear as two neighboring indepen-dent neoplasms that coexist with no or minimal intermingling (collision tumors) or as two intermingled malignant endocrine and non-endocrine cell types (composite carcinomas). 3,4 MiNENs arising in an intestinal inflammatory context are unusual. We briefly reported the clinical context of the first case of MiNEN originating in Crohn's disease (CD). 5 Since then, we became interested in elucidating the pathogenesis of MiNENs by identifying their respective precursor lesions. To determine the pathogenesis of MiNENs arising in CD, we used a comprehensive morphomolecular approach, including next-generation sequencing (NGS) obtained through selec-tive macrodissection of the MiNEN components and their respective precursors. To our knowledge, there are a few reports of gastric or colonic MiNENs using this original approach; 6 – 10 however, these reports are not comparative studies on precursor lesions. Here we reported on a 44-year-old man