Keratin expression in normal skin and epidermal neoplasms demonstrated by a panel of monoclonal antibodies

The tissue labelling of a panel of monoclonal antikeratin antibodies (LL001, LL002, LL003, LP2K, BA17, LP34, CAM5.2, and LH1) recognising keratins 1, 5, 8, 10, 14, 18, and 19 were investigated in frozen and formalin-fixed normal skin. Antibodies LL001, LL003, BA17, LP34, CAM5.2, and LH1 were found to be reactive in formalin-fixed material and were used to study 23 basal cell carcinomas, 8 squamous cell carcinomas, 5 keratoacanthomas, 5 Bowen's disease, and 6 clear cell acanthomas. All these tumours demonstrated a loss of keratin 10 expression as demonstrated by loss of labelling with LH1. Keratin 14 expression, as demonstrated by LL001, was reduced but present in all the tumours except squamous cell carcinomas and keratoacanthomas where increased labelling was observed in the more differentiated areas of these tumours. Simple epithelial keratin expression was demonstrated by positive labelling with CAM5.2 and keratin 19 by BA17 in a third of basal cell carcinomas and squamous cell carcinomas. Three of the five keratoacanthomas labelled with BA17, indicating the presence of keratin 19 in these lesions. These results support the concept that keratin expression is a phenotypic marker of the state of differentiation or malignant transformation and that patterns of keratin expression are not specific to any particular premalignant or malignant disorder.