Mesenteric Castleman Disease Misdiagnosed as Lymph Node Metastasis of Rectal Cancer on 18 F-FDG PET/CT.

Two years ago, a 64-year-old man underwent an 18 F-FDG PET/CT for staging rectal cancer. Besides the hypermetabolic rectal lesion, the image revealed a mesenteric lymph node with intense activity and multiple lung nodules with slight FDG uptake, which were highly suspected of metastases. After surgery and multiple cycles of chemotherapy, the follow-up 18 F-FDG PET/CT showed remission of all lesions except for the enlarged mesenteric lymph node with higher metabolic activity. Serum CEA remained normal during the follow-up. Postoperative pathology of the mesenteric lymph node confirmed Castleman disease.