Low back pain is a very common symptom, caused mostly by acute or chronic injuries, such as fractures, sprains, lumbar muscle strain, lumbar dorsal fascia fibrositis, lumbar disc prolapse or infectious inflammation of the lumbar spine and degenerative osteoarthrosis. Only in a few cases, the possibility of tumor should be considered. Therefore, there is no need to be afraid of cancer when lumbar pain occurs. However, if low back and leg pain occurs in the following cases, we should be alert to the existence of tumor. 1.Children complain of persistent low back and leg pain, and pressure or percussion on the local area also causes obvious pain and avoidance reaction, and one or two legs are often swollen and numb, and the pain may cause sudden inability to move the lower limbs. 2. Adolescents aged 15-25 often complain of low back and leg pain, which is mild at first and then gradually increases, especially at night. Compression or percussion of the lumbar region often causes pain to increase, and spasm of the muscles next to the lumbar vertebrae may cause restriction of spinal movement or bending of the spine to one side, accompanied by numbness or pain in the lower limbs. 3. Normally, there are manifestations of lumbar and leg pain, and the lower extremities suddenly appear for no reason with symptoms of paralysis such as urinary and fecal disorders and decreased muscle strength. The paralysis is transient and can be relieved automatically after lasting for a period of time. 4.With a history of low back and leg pain, the sacrum (tailbone) has recently been protruding or bulging, with a sense of elasticity, and causes significant pain when pressing on the local area. Rectal irritation symptoms may also appear, i.e., there is often a sensation of internal and external bowel movement, but each time it does not come out. 5.Lower back pain develops rapidly to the point of unbearable and severe pain, which is aggravated at night and makes it difficult to sleep, and strong painkillers must be used. Local pressure pain, percussion pain and limitation of movement, numbness or pain in the lower limbs, general condition failure, and showing malignant-like manifestation. 6.Persistent back and leg pain, gradually aggravated, and generalized bone pain. Sudden fracture of ribs and limb bones without obvious traumatic causes. 7.With lung cancer, prostate cancer, esophageal cancer and other cancers. Recently, there is severe pain in the back and legs with restricted activities, which is slightly relieved during the day and intensified at night, requiring painkillers. This often suggests that the above cancers have the possibility of metastasis on the waist and legs. In the above situation, you should go to the hospital for further examination, such as X-ray, CT scan, MRI and other tests, in order to clarify the diagnosis and provide symptomatic treatment.