HMB45 (Human Melanoma Black) refers to a specific monoclonal antibody clone that targets the gene PMEL and has high sensitivity for identifying melanoma in immunohistochemistry. PMEL itself is a transmembrane glycoprotein found in pigment cells of the skin and eye, and antibodies to PMEL including HMB45 are often used as melanocyte markers. The clone HMB45 is not present in all melanomas, with detection rates of between 50 to 70%. It is positive in melanocytes in the skin, nevi, junctional nevus cells, and fetal melanocytes, and in cancer it is positive in melanomas and angiomyolipomas. References: PLoS ONE. 2011. 6: e18784, PMID: 21526207; Am J Pathol. 1986;123:195, PMID: 3518473; Modern Pathology. 2002. 15 (12): 1288–1293, PMID: 12481009