The usefulness of tyrosinase in the immunohistochemical assessment of melanocytic lesions: a comparison of the novel T311 antibody (anti-tyrosinase) with S-100, HMB45, and A103 (anti-melan-A)

Aim-To compare the sensitivity and staining pattern of the new immunohistoc hemical antibody to tyrosinase (T311) with S-100, HMB45, and the recently e valuated antibody to melan-A (A103) in a range of melanocytic lesions. Method-Archival, formalin fixed, paraffin wax embedded sections from 50 ben ign and malignant melanocytic lesions were stained immunohistochemically wi th anti-tyrosinase, A103, S-100, and HMB45. They were scored semiquantitati vely for the distribution and intensity of staining. Results-All melanomas, with the exception of desmoplastic melanoma, showed some staining with all four antibodies. Overall, T311 and A103 showed an in termediate sensitivity compared with that of S-100 and HMB45. T311 stained most benign and malignant lesions strongly and diffusely with minimal backg round staining. Immunoreactivity was found to be patchy in some naevi, with weak or absent staining of the mature melanocytes. A103 showed strong and diffuse staining of all benign lesions and most melanomas with minimal back ground staining. S-100 was the most sensitive, with diffuse staining of mos t lesions, including desmoplastic and metastatic melanoma, but lacked speci ficity. HMB45 was the least sensitive antibody, frequently demonstrating pa tchy staining with absent staining in some benign naevi. Conclusions-S-100 remains the most sensitive marker of melanocytes. However , because of its lack of specificity, it should be used with at feast one o ther more specific antibody. HMB45 is more specific, but lacks sensitivity; T311 is a reliable marker of melanocytes in paraffin wax embedded sections and is worth consideration for use in a staining panel, although it shows no additional benefit over A103.