One day last year, an old man came to my clinic and said to me happily, “Thank you, Dr. Zhang, thanks to your reminder, my partner went for a gastroscopy and found stomach cancer, which had just been operated in the gastrointestinal surgery. It turns out that more than a month ago, the old couple came to my clinic and said that the old lady suddenly had swollen legs. After examination, it was found that it was deep vein thrombosis in the lower extremity. While I prescribed the routine examination and treatment, I asked the old man to do tumor screening, and early gastric cancer was found. One day, a middle-aged woman came to the outpatient clinic with sudden swelling at the base of the left neck and left upper limb, and a venous ultrasound was done, suggesting left subclavian vein thrombosis. The patient approached me with the report, and I could not help but be alerted. I asked in detail whether there was any change in diet and stool in the recent period, and whether there was any wasting and weakness. The patient said no, and there was no special condition in gynecology. I began to examine her while asking questions, and found that the left neck was swollen, and I could feel some small bumps with a hard texture. An abdominal examination followed and no abnormality was found. Based on my years of experience, I asked the patient to undergo tumor screening, prescribed blood draw for tumor markers and abdominal ultrasound, and recommended the patient to go to gastroenterology and gynecology for examination. A week later the patient came back with the report with two elevated tumor markers and abdominal ultrasound revealed multiple enlarged retroperitoneal lymph nodes. The patient was asked to have a gastrointestinal examination as soon as possible. Another week, the patient’s colonoscopy revealed an ileocecal mass. At this point, the cause of deep vein thrombosis was finally clear: it was caused by a tumor from the gastrointestinal tract. With the popularization of medical knowledge, more and more people are now aware of the danger of venous thrombosis and pulmonary embolism. However, they do not know another layer of deep vein thrombosis – tumor markers. There are many causes of deep vein thrombosis, but they can be broadly categorized into three main groups: blood stagnation, altered blood composition, and vascular injury. Economy class syndrome caused by long-distance travel is caused by deep vein thrombosis in the lower extremities, and the main cause is lack of movement of the lower extremities and stagnation of blood flow. After trauma or surgery, the body mobilizes coagulation reactions and blood composition is altered. Trauma or surgery may also cause direct or indirect damage to blood vessels and participate in thrombosis. After the occurrence of tumor, it can secrete some substances by itself, leading to the alteration of blood composition. In addition, the response of immune mechanism caused by tumor can also produce some substances, such as: interleukin 1 and tumor necrosis factor can induce fibrin deposition through the combination of procoagulant expression of vascular endothelial cells and fibrinolytic inhibition, and tumor necrosis factor can even make the most important by prompting the down regulation of endothelial thrombomodulin expression. naturally occurring anticoagulation mechanisms. The tumor itself or its metastatic lymph nodes can also compress the veins leading to impaired venous blood return and stagnation of blood flow, further promoting thrombosis. Foreign textbooks clearly state that more than 50% of patients with venous thrombosis have an underlying malignant disease. Many doctors have also heard the phrase: deep vein thrombosis is a tumor marker. In my opinion, it is not only a marker, but also a possible last call for help from the body. Perhaps the black stool, weakness, emaciation, anemia …… have failed to attract your attention before, and now you are reminded again through the high swelling and pain of the limbs, if you still don’t pay attention to it, you may lose the last chance to cure the tumor. However, due to the limitation of current clinical diagnosis technology, sometimes it is not always possible to detect tiny tumor lesions in time. For the elderly, a negative screening test is not enough to rest on your laurels, and must be reviewed again at a later time. As a vascular surgeon, we should not only be satisfied with the diagnosis of DVT, but also ask more questions, especially for the elderly patients, the investigation of the cause of DVT should be the focus of clinical diagnosis. As a patient, you should fully trust the doctor’s judgment and actively cooperate with the examination, so that you can seize this fleeting opportunity in time to save your health.