Keratin and involucrin immunohistochemistry of nasopharyngeal carcinoma

Forty nasopharyngeal carcinomas (NPC) were studied by immunohistochemistry using an antibody to involucrin and the following three keratin antibodies: (1) an antibody to low molecular weight keratin reactive with nonsquamous epithelium, (2) a high molecular weight keratin antibody reactive with suprabasal squamous epithelium, and (3) a keratin antibody reactive with full thickness stratified epithelium. In its pattern of reactivity, the last antibody overlaps the low and high molecular weight keratin antibodies and is used as a broad spectrum keratin antibody. By World Health Organization (WHO) classification, the cases in this article included eight keratinizing squamous cell carcinomas, eight nonkeratinizing carcinomas, 20 undifferentiated carcinomas, and four adenocarcinomas. The antibody to broad spectrum keratin had an overall sensitivity of 87.5% and was positive in all eight keratinizing squamous cell carcinomas, seven nonkeratinizing carcinomas (87.5%), 18 undifferentiated carcinomas (90%), and two adenocarcinomas (50%). Low molecular weight keratin antibody stained one additional NPC, which was negative when broad spectrum keratin antibody was used. Involucrin and high molecular weight keratin antibodies demonstrated near parallel staining in all histologic classes; there was marked localization to areas of squamous differentiation. While involucrin is a marker for foci of greater squamous differentiation, broad spectrum keratin antibody may aid in the diagnosis of all histologic subtypes of NPC.