Patients with digestive tract tumors will have some other symptoms besides the tumor itself, such as upper abdominal discomfort, which is often referred to as the accompanying cancer syndrome. This situation occurs mainly because the tumor cells can secrete many substances, and these factors can damage several organs and cause damage to other systems. For patients with gastric cancer, the more common one is anemia, mainly because the tumor itself breaks down and causes bleeding, resulting in anemia. In addition, it can affect the absorption of folic acid, leading to insufficient raw materials for blood production and causing anemia. In addition, some of our cytokines also act on the skin, causing, for example, seborrheic dermatitis or skin damage, and pain in muscles and joints. In addition, the action on the peripheral nervous system can cause a decrease in peripheral nerve perception, or numbness and mobility problems. More importantly, the effect on the kidneys can cause glomerular damage and nephrotic syndrome, resulting in proteinuria or edema. Therefore, more patients come to the clinic not because of the symptoms of the primary lesion, such as upper abdominal discomfort, but because of the associated cancer syndrome. Therefore, if these abnormal symptoms occur, please seek prompt examination by a specialist.