Uncommon Tumor, Unusual Site, and Unconventional Behavior: Report of a Gastric Composite Gangliocytoma/Neuroma and Neuroendocrine Tumor (CoGNET) With Metastases.

With the 2022 WHO Classification of Neuroendocrine Neoplasms1 came an important distinction between epithelial and non-epithelial neoplasms, and the possibility of composite tumor in certain organs, including the duodenum, the spine and the middle ear. In particular, the formerly termed gangliocytic paraganglioma of the duodenum has been renamed as "composite gangliocytoma/neuroma and neuroendocrine tumor (CoGNET)." We present an unusual CoGNET arising in the stomach, displaying distinctive histomorphologies in primary tumor and metastases. Additionally, we discuss diagnostic pitfalls and highlight the importance of recognizing the combined features that can be seen in this rare, potentially malignant, entity.