CD10, also known as membrane metalloendopeptidase, neutral endopeptidase, neprilysin and common acute lymphoblastic leukaemia antigen (CALLA), is a zinc-dependent metalloendoprotease that cleaves signaling peptides. It is widely expressed in various normal tissues and in epithelial, stromal or both components of various malignancies. CD10 is a marker for intestinal epithelial brush border. It is also present in normal bile ducts and gallbladder epithelia but is absent in cholangiocarcinomas. It is con-sidered as the prototype of this family of membrane-bound, zinc-dependent endopeptidases, which regulate the physiological action of various peptides by lowering their extracellular concentration available for receptor binding. CD10 is also known to be an amyloid b-peptide (Ab) degrading enzyme. Polymorphisms in the CD10 gene increase the risk for Alzheimer disease. Outside the nervous system, it is present on the surface of neutrophils and regulates their activation by degradation of in ammatory peptides.