Involucrin is expressed in a range of stratified squamous epithelia, including the cornea. In normal epidermis, it is first expressed in the upper spinous layers, and in keratinocyte cultures it is expressed by all cells that have left the basal layer. Involucrin expression is abnormal in squamous cell carcinomas and premalignant lesions, and is reduced in severe dysplasias of the larynx and cervix.