Description
Melanocytes produce organelles called melanosomes which produce melanin, the pigment that gives color to skin, hair, eyes, scales and feathers. gp100 was identified in an attempt to clone the gene Tyrosinase, an enzyme required for melanin synthesis. Further testing determined that gp100 is a melanoma-specific protein and is responsible for melanosome maturation, facilitating the transition from amorphous rounded vesicles to fibrillary ellipsoid organelles.
Metastatic amelanotic melanoma can often be confused with a variety of poorly differentiated carcinomas, large cell lymphomas, and sarcomas using H & E stains alone. It is also difficult to differentiate melanoma from spindle cell carcinomas and various types of mesenchymal neoplasms. Clone HMB45 gp100 antibody stains fetal and neonatal melanocytes, junctional and blue nevus cells, and malignant melanoma. It also stains angiomyolipomas, tumors most commonly associated with the kidney. Intradermal nevi, normal adult melanocytes, and non-melanocytic cells are negative. This gp100 antibody does not stain tumor cells of epithelial, lymphoid, glial, or mesenchymal origin.
The gp100 molecule is a 100kDa glycosylated protein that is cleaved into a small (26kDa) carboxy-terminal fragment and a larger amino- terminal section (60-64 kDa), which is subsequently cleaved to generate 26kDa and 34-38kDa fragments