The HMB45 clone reacts with a
neuraminidase-sensitive oligosaccharide side chain of a glycoconjugate present
in immature melanosomes. The HMB45-reactive antigen is present in cutaneous
melanocytes, prenatal and infantile retinal pigment epithelium and melanoma
cells. It is also thought to be oncofetal in nature. This antibody has been
shown to label the majority of melanomas. The MART-1/Melan A recognizes a
protein of 18kDa, identified at MART-1 (Melanoma Antigen Recognized by T cells
1) or Melan-A. Melan-A is a useful addition to melanoma panels which is specific
to melanocytic lesions. Studies have also shown that MART-1 is more sensitive
than HMB45 when labeling metastatic melanomas. Tyrosinase is a key enzyme
involved in the initial stages of melanin biosynthesis. Studies have shown
Tyrosinase to be a more sensitive marker when compared to HMB45 and MART-1. It
has also been shown to label a higher percentage of desmoplastic melanomas than
HMB45. The combination of HMB45, MART-1 and Tyrosinase make this quadruple
antibody combination a first-order pan melanoma screener, and may prove to be a
valuable marker for melanoma metastasis in sentinel lymph
nodes.