T311 - An anti-tyrosinase monoclonal antibody for the detection of melanocytic lesions in paraffin embedded tissues

Tyrosinase is a key enzyme in melanin biosynthesis and represents a marker of melanocytic differentiation. We previously generated T311 a murine monoc lonal antibody body to the tyrosinase recombinant protein. This study was p erformed to evaluate T311 as a diagnostic immunohistochemical reagent for u se on formalin-fixed paraffin embedded pathological material. We analyzed t he specificity of the antibody on a panel of normal and neoplastic tissues, and we assessed its sensitivity in a large number of metastatic and primar y malignant melanomas, nevi, three angiomyolipomas, and two vitiligo specim ens. T311 revealed intense reactivity on paraffin-embedded material. Immuno reactivity was limited to cells of melanocytic differentiation and no immun ostaining was present in unrelated normal tissues and tumors. Eighty four p ercent of metastatic malignant melanomas were immunoreactive with T311 and showed predominantly a homogeneous expression pattern. However, in primary melanomas of the desmoplastic/spindle cell type, T311 revealed a poor immun oreactivity. Nevi showed intense staining at the junctional zone, while the dermal component revealed decreasing reactivity towards deeper areas. Only one angiomyolipoma was focally immunoreactive with T311. Vitiligo specimen s were immunonegative. We conclude that T311 is a specific and sensitive ma rker for the detection of melanocytic lesions in formalin-fixed paraffin-em bedded tissues and a useful serological reagent for diagnostic pathology.