A rare case of urachal mucinous adenocarcinoma detected by 18F-FDG PET/CT.

A 48-year-old woman presented with abdominal pain, and her initial investigations, which included an abdominal ultrasound and a pelvic MRI examination, revealed a dominant soft tissue mass abutting her left iliac bone, extensive pelvic adenopathy, and multiple osseous metastases. The findings were concerning for chondrosarcoma; however, biopsy results were consistent with mucinous carcinoma of unknown origin. A staging 18F-FDG PET/CT revealed a mildly FDG-avid soft tissue mass with scattered calcifications extending to the dome of the urinary bladder, highly suggestive of a primary tumor. Cystoscopy with tissue sampling of this mass demonstrated a primary mucinous adenocarcinoma of the urachus.