Can HLA-DR expression help in the routine diagnosis of malignant melanomas?

Two monoclonal antibodies, TAL-IB5 and LN3, directed at epitopes of HLA-DR were applied to a variety of benign naevi and malignant melanomas. Of the 31 naevi examined, 28 were completely unreactive. Weak staining was confined to a few cells in two intradermal naevi and there was more widespread reactivity in a halo naevus. Seven of the 25 primary cutaneous malignant melanomas were reactive with one or both of the antibodies and this reactivity was more marked in the deeper lesions. These positive cases were not felt to present diagnostic difficulties and it was concluded that TAL-IB5 and LN3 were not of use in distinguishing between benign and malignant melanocytic proliferations.