There are several possible causes of leg swelling in patients with cancer. If the swelling is confined to one side of the leg, it may be localized to suspect whether it is a combination of lower limb venous thrombosis. If it is bilateral limb swelling, there is no possibility of edema caused by hypoproteinemia, or pelvic tumor compressing to the veins, and the return obstacle causes double lower limb swelling. In this case, do pelvic CT examination, can be found in the pelvis of the occupying lesion, can be clear. If it is hypoproteinemia, draw blood to check liver function, found that the albumin is significantly reduced, it can be clear whether it is edema caused by hypoproteinemia. Other causes such as renal failure, hepatic failure or cardiac failure can cause leg swelling. There are more causes of leg swelling in cancer patients, depending on whether it is bilateral limbs or unilateral limbs.