An immunohistochemical study of sebaceous carcinoma with anti-keratin monoclonal antibodies: comparison with other skin cancers.

Formalin-fixed and paraffin-embedded tissue specimens of six cases of extraocular sebaceous carcinoma were studied immunohistochemically with eight anti-keratin monoclonal antibodies, 34 beta B4, 35 beta H11, Ks13.1, Ks19.1, PKK1, LP34, KL1 and AE1. The staining patterns of sebaceous carcinoma were compared with those of normal sebaceous glands and other skin cancers which should be distinguished from sebaceous carcinoma histopathologically. The other skin cancers compared were eccrine porocarcinoma, malignant clear cell hidradenoma, extramammary Paget's disease with underlying adenocarcinoma, malignant trichilemmoma, and squamous cell carcinoma. Most cases of sebaceous carcinoma were stained with 35 beta H11, Ks19.1, LP34, KL1 and AE1, while normal sebaceous glands were positive only with 35 beta H11, LP34, KL1 and AE1. By immunostaining, sebaceous carcinoma was distinguishable from extramammary Paget's disease with underlying adenocarcinoma, squamous cell carcinoma, malignant trichilemmoma, and eccrine porocarcinoma, but was not clearly distinguishable from malignant clear cell hidradenoma. These findings demonstrate that sebaceous carcinoma shows positive reactions with antibodies to simple epithelial keratin, probably as a result of neoplastic transformation, and that immunohistochemical examination using anti-keratin monoclonal antibodies is useful in distinguishing sebaceous carcinoma from several other skin cancers.