FDG uptake in tumor thrombus in inferior vena cava from rectal cancer on positron emission tomography.

A 74-year-old woman with a history of rectal carcinoma underwent whole body combined positron emission tomography/computed tomography (PET/CT) scanning for staging. Diffuse intense FDG uptake was seen in the distended infrarenal inferior vena cava (IVC) extending to the bilateral common iliac and left external as well as internal iliac veins. Heterogeneous hyperdense material was seen on the corresponding CT scan, suggesting tumor thrombus. Tumor thrombus shows increased FDG uptake resulting from the increased glycolytic rate in malignant cells.