Mesenteric paraganglioma mimicking nodal metastasis of an occult small intestinal neuroendocrine tumor

Summary Paragangliomas (PGLs) are rare neuroendocrine neoplasms of neural-crest origin, with primary mesenteric localization representing an exceptionally uncommon entity that is rarely considered in the preoperative differential diagnosis of mesenteric masses. We report the case of a 51-year-old woman who was referred to our institute following the incidental detection of a 12 × 9 mm hypervascular nodule within the pelvic small bowel mesentery on contrast-enhanced computed tomography (CT). Subsequent 68 Ga-DOTATOC positron emission tomography/CT showed intense somatostatin receptor uptake confined to the mesenteric nodule, with no other lesions. Dedicated pan-colonoscopy was unremarkable and 24-h urinary 5-hydroxyindoleacetic acid was within normal limits. Preoperative diagnosis of nodal metastasis from an occult ileal neuroendocrine tumor was made, and laparoscopic surgery was undertaken. Meticulous bimanual palpation of the small bowel with transillumination did not reveal any primary lesions, while a 1 cm mesenteric mass was identified and excised. Histology revealed a solid tumor with Zellballen architecture with tumor cells positive for chromogranin A and GATA3, and negative stains for cytokeratin, CDX2, and serotonin, establishing the diagnosis of paraganglioma. This case highlights the importance of recognizing paraganglioma as a potential diagnostic mimic in solitary somatostatin receptor-avid mesenteric nodules to prevent unnecessary investigations and guide appropriate surgical management. Learning points Primary mesenteric paragangliomas should be considered in the differential diagnosis of solitary, hypervascularized mesenteric masses. A solitary SSTR-avid mesenteric nodule in an asymptomatic, biochemically silent patient does not necessarily imply nodal metastasis from an occult small intestinal neuroendocrine tumor. Considering alternative diagnoses may avoid unnecessary endoscopic, radiological, and surgical investigations for an intestinal primary lesion. Definitive diagnosis and risk stratification rely on histopathology and immunohistochemistry, including epithelial markers, GATA3, and SDHB. Awareness of mesenteric paraganglioma as a diagnostic mimic can prevent overtreatment and guide appropriate surgical management.