18F-fluorodeoxyglucose positron emission tomography/computed tomography in extensive bland portal vein thrombosis from retroperitoneal adenocarcinoma.

A 73-year-old woman undergoing hormone therapy for previously treated localized breast cancer presented at oncology follow-up 4 years after mastectomy/radiation therapy with weight loss, night sweats, and abdominal pain. Contrast computed tomography (CT) abdomen revealed a soft-tissue mass posterior to the pancreas, several enlarged retroperitoneal lymph nodes, and a dilated portal vein. On 18F-fluorodeoxyglucose positron emission tomography/CT, metabolic activity extended along the portal vein, outlining most of the liver venous system. This "tree-like" appearance was diagnostic of recent portal vein thrombosis by vascular compression from the retroperitoneal mass. Biopsy of the mass later confirmed undifferentiated adenocarcinoma without breast cancer marker expression.