Patients with high leucine aminopeptidase are often considered to have biliary obstruction or tumor disease of the liver. Leucine aminopeptidase, abbreviated as LAP in our tests, is a protein enzyme. When patients have biliary stasis in the extrahepatic bile ducts or extrahepatic biliary obstruction, the patient’s LAP will be significantly increased, which is usually about 2-4 times the normal value; when the patient’s obstruction is more obvious, the value can generally rise to more than 5 times. For some patients with neoplastic diseases, the LAP in the blood and urine may be significantly increased; for some extrahepatic tumors, such as breast cancer or gynecological system, the LAP may also be significantly increased. For some extrahepatic tumors, such as breast cancer or gynecologic system tumor disease, the LAP may also be significantly elevated. In this case, patients should actively review the LAP, especially after the tumor, patients need to review the LAP in time during chemotherapy, which can reflect whether the tumor has recurred.