Human Melanoma Black 45 (HMB-45) is an antibody used as an IHC reagent has often been labeled as a marker for melanoma, even though some benign lesions have been noted to show positive staining reactions with this reagent. In IHC assays, this HMB-45 reacts with melanoma cells, junctional nevus cells, and fetal melanocytes but generally not with completely melanized normal adult melanocytes or with intradermal nevus cells. Except some rare tumors showing evidence of melanogenesis (clear cell sarcoma, pigmented schwannoma) or tumors associated with tuberous sclerosis complex, HMB 45 is non-reactive with almost all non-melanoma malignancies. HMB-45 in sentinel lymph nodes is considered to have low false-positive results because of its good resolution and low background staining.