Mesenteric unicentric Castleman’s disease misdiagnosed as gastrointestinal neuroendocrine tumour

Castleman's disease is a rare lymphoproliferative disorder with a variable presentation ranging from no clinical symptoms to fever and fatigue. We report a case of a male in his 30s who presented to the emergency department with non-specific symptoms, including fever, cough, diarrhoea, abdominal pain and findings of bloody mucus in his stool. Preoperative imaging using CT showed a hypervascular mass in the abdomen measuring 3.9 cm. Positron emission tomography with Gallium-68 DOTA-Tyr³-octreotate (DOTATATE) showed moderate radiotracer uptake, raising suspicion for a neuroendocrine tumour. Preoperative endoscopic ultrasound biopsy results showed a benign reactive lymph node. The patient's case was discussed at a multidisciplinary tumour board, where diagnostic/therapeutic resection was advised. Following resection of the mass, it was found to be an enlarged lymph node with histopathological features consistent with hyaline vascular Castleman's disease. The patient did not experience any complications, postoperative imaging was unremarkable, and he is being monitored closely for recurrence.