Collision tumor: pigmented Bowen's disease and seborrheic keratosis

Abstract: Bowen's disease is a type of squamous cell carcinoma in situ of the skin. The pigmented form is rare and represents less than 2% of cases. We report a case of a 74-year-old black man with a blackened and asymptomatic leg injury for about 6 months. Clinically, and under dermatoscopy, the injury was suggestive of melanoma or melanoacanthoma, and a definitive diagnosis was made by histopathological examination.