Are differences in filaggrin expression suitable for discriminating benign, premalignant and malignant skin lesions?...

The differential diagnosis of benign and malignant skin lesions may pose considerable difficulties. Therefore, 137 formalin-fixed paraffin-embedded biopsies of various benign, premalignant and malignant skin tumours were examined immunohistochemically for the presence of filaggrin using the monoclonal anti-filaggrin antibody AKHl. The proliferating cells of both benign and malignant tumours were negative for filaggrin. Most of the benign tumours exhibited an intense filaggrin-positive granular layer identical to the adjacent healthy skin whereas benign conditions such as irritated seborrhoeic keratoses and clear cell acanthomas were completely devoid of filaggrin. Keratoacanthomas revealed an inconsistent staining pattern for filaggrin. Premalignant and malignant lesions including basal cell carcinomas were either focally positive or completely negative for filaggrin. The absence or presence of filaggrin in these lesions did not correspond to the degree of dysplasia. Moreover, none of these conditions gave a staining pattern for filaggrin to be used for the histological differential diagnosis of these skin lesions.