Keratin and filaggrin expression in keratoacanthoma

To clarify the histogenesis of keratoacanthoma, we studied keratin (K) expression in keratoacanthoma (KA) using 10 different anti-keratin antibodies against K1, K7, K8, K10, K14, K15, K16, K17, K18 and K19 and anti-filaggrin (filament aggregating protein) antibody. In the centre of KA, K1 and K10 expressions were declined, and K14 and K16 were detected in the tumour cells, suggesting differentiation towards the outer root sheath beneath the orifice of the sebaceous duct. These results suggest that KA differentiates towards the outer root sheath beneath the opening of the sebaceous duct.