Synchronous small bowel neuroendocrine tumour, colonic adenocarcinoma, and non-Hodgkin lymphoma: a rare triad of primary malignancies

A man in his 70s presented to the Emergency Department with a history of progressive dyspnoea and was found to be anaemic. Endoscopic evaluation revealed a caecal lesion, confirmed histologically as a moderately differentiated adenocarcinoma. Staging computed-tomography imaging demonstrated widespread lymphadenopathy including pelvic, mediastinal and axillary regions, that appeared unlikely to be related to the colonic primary. Surgical resection of the right colon and a palpable axillary node was performed, during which a separate jejunal lesion was incidentally identified and resected. Histopathological analysis confirmed three distinct neoplasms: colonic adenocarcinoma, a small bowel neuroendocrine tumour, and non-Hodgkin lymphoma. Immunohistochemical and molecular profiling confirmed independent origins with no shared clonal relationship. The following case highlights the diagnostic and therapeutic challenges posed by synchronous multiple primary malignancies, particularly across divergent tissue lineages. Accurate histopathological distinction and multidisciplinary coordination are essential to guide management, prioritize treatment, and optimize patient outcomes in such exceptional presentations.