The diagnostic use of low molecular weight keratin expression in sebaceous carcinoma

Sebaceous carcinoma is an infrequent skin tumor and its histological features sometimes closely resemble those of squamous cell carcinoma (SCC) and basal cell epithelioma (BCE), which often leads to a misdiagnosis. In the present immunohistochemical study, however, sebaceous carcinoma exhibited quite a different expression of keratins from SCC and BCE. We immunohistochemically examined 26 excised specimens of sebaceous carcinoma, 10 of SCC and 12 of BCE of the eyelids, using two monoclonal antibodies against high molecular weight keratins, 34 beta B4 (68kd) and 34 beta E12 (56kd, 56.5kd, 58kd), and two monoclonal antibodies against low molecular weight keratins, 35 beta H11 (54kd) and CAM5.2 (39kd, 43kd, 50kd). The cases of sebaceous carcinoma were positive with 34 beta B4 (23%), 34 beta E12 (54%), 35 beta H11 (81%) and CAM5.2 (73%). Of the four anti-keratin antibodies used in this study, 35 beta H11 was negative in all cases of SCC or BCE. These findings indicate that when sebaceous carcinoma is suspected, but no fat staining appropriate materials are available, a monoclonal antibody against low molecular weight keratin, 35 beta H11 (54kd), can be a useful tool to immunohistochemically rule out both SCC and BCE.