Single jejunoileal and right colonic carcinoids as midgut tumors. A study collating immunophenotypes and histogenesis

The jejunoileum and the right colon, both of which are located in the midgut, have some histologic similarities such as the presence of Paneth cells and intraepithelial endocrine cells (IEECs). Since gastrointestinal (GI) carcinoids arise from the same stem cells as GI endocrine cells, the question was whether or not there might also be similarities in the histogenesis of jejunoileal carcinoids (JICs) and right colonic carcinoids (RCCs). Ten single JICs and 3 RCCs together with their respective controls were stained using various neurohormonal immunoreagents. Our results showed that neither the JICs nor the RCCs appeared to arise from a background of diffuse IEEC hyperplasia. Furthermore, in the jejunoileum, serotonergic progenitor cells appear to have a proclivity for neoplastic transformation, as do cells of the pancreatic polypeptide and glucagon lineage in the right colon.