A few days ago, a juvenile patient was seen in the orthopaedic clinic whose main symptom was localized vague pain below the left knee, which was worse at night. The radiographs showed variable bone density and irregular destruction, and the alkaline phosphatase was significantly increased. The preliminary diagnosis was: bone malignant tumor, and the patient was instructed to further clarify the examination and pathological examination in time. It was also introduced that alkaline phosphatase is valuable for diagnosing benign and malignant bone tumors. Alkaline phosphatase ( ALP ) is an enzyme widely distributed in human liver, bones, intestines, kidneys and placenta and other tissues excreted to the outside of the bile through the liver. However, it is not a single enzyme, but a group of isoenzymes. Six isoenzymes, AKP1, AKP2, AKP3, AKP4, AKP5 and AKP6, have been identified. The first, second and sixth are from the liver, the third from bone cells, the fourth from placenta and cancer cells, and the fifth from small intestinal villous epithelium and fibroblasts. Serum ALP is mainly of hepatic and skeletal origin. Most of the serum in growing children is derived from osteoblasts and growing osteochondrocytes, with a small amount from the liver. Alkaline phosphatase is mainly used in the screening of obstructive jaundice, primary hepatocellular carcinoma, secondary hepatocellular carcinoma, and cholestatic hepatitis. In these diseases, hepatocytes overproduce ALP, which enters the bloodstream via the lymphatic tract and hepatic sinusoids, and at the same time, serum alkaline phosphatase is significantly elevated due to impaired bile excretion from the intrahepatic biliary tract and backflow into the bloodstream. However, this enzyme is also active in bone tissue. Therefore, pregnant women, healing fractures, osteochondrosis. In rickets, osteoclastic carcinoma, osteoporosis, liver abscess, liver tuberculosis, hepatic sclerosis, leukemia, and hyperthyroidism, serum alkaline phosphatase may also be elevated and should be differentiated. Normal range (continuous monitoring method) Females, 1-12 years old, less than 500 U/L; greater than 15 years old, 40-150 U/L; Males, 1-12 years old, less than 500 U/L; 12-15 years old, less than 750 U/L; greater than 15 years old, 40-150 U/L. Clinical significance 1. Physiological increase: In children during the physiological skeletal development, alkaline phosphatase activity can be 1 to 2 times higher than normal. 1 to 2 times higher. (2) Pathological increase: (1) Skeletal diseases such as rickets, chondromalacia, bone malignancy, malignant tumor bone metastasis, etc.; (2) Hepatobiliary diseases such as extrahepatic biliary obstruction, hepatocellular carcinoma, cirrhosis, capillary biliary hepatitis, etc.; (3) Other diseases such as hyperparathyroidism. (3) Pathological decrease: seen in severe chronic nephritis, childhood thyroid insufficiency, anemia, etc. In the study, it was also found that serum TALP and BALP were significantly higher in the group of patients with malignant bone tumors than in the group of patients with benign bone tumors; serum TALP and BALP levels decreased significantly after surgical treatment. And it was found that both serum TALP and BALP are another sensitive and easy biochemical index for clinical diagnosis and condition monitoring of bone tumors, and the sensitivity and specificity of serum BALP is higher than that of serum TALP.