Reactivity of monoclonal antibody OKM5 with sebaceous carcinoma

Two cases of sebaceous carcinoma (SC), as well as epithelial tumours, melanoma, and lymphoma, were examined using immunoperoxidase and a panel of monoclonal antibodies on cryostat sections. The results showed that, whereas all SC cells in both cases reacted strongly with monoclonal antibody OKM5, other tumour cells (except juvenile xanthogranuloma cells) did not. The pagetoid cells within the epidermis of SC also reacted with OKM5 antibody. Although the nature of the phenomenon merits further study, this reactivity, or cross-reactivity, might possibly aid diagnosis of SC.