An Asymptomatic Urachal Mucinous Adenocarcinoma on FDG PET/CT

A 42-year-old man presented with an incidentally discovered, elevated serum carcinoembryonic antigen (CEA) level. Although colonic polyps were identified and removed through polypectomy, his CEA level remained persistently elevated. Subsequent CT revealed a cystic-solid mass in the midline upper pelvis, raising suspicion for malignancy. Staging FDG PET/CT demonstrated increased FDG avidity in the known mass, with no evidence of metastasis. The lesion was surgically resected, and histopathologic analysis confirmed a rare urachal mucinous adenocarcinoma. The patient recovered well postoperatively. Urachal mucinous adenocarcinoma should be considered in the differential diagnosis of hypermetabolic midline pelvic masses on FDG PET/CT imaging.