A form of squamous cell carcinoma in situ. It is a distinct clinicopathological entity and arises from the skin or the mucocutaneous junction. It affects predominantly white males in their 6-8th decades of life. Exposed and non-exposed skin sites are equally affected. UV damage and ingestion of inorganic arsenic may play a role in the development of the disease. On the skin surface, it presents as a single or multiple erythematous, scaly, keratotic patches or plaques. The clinical entity of erythroplasia of Queyrat is regarded as Bowen disease of the penis and it presents as an asymptomatic, red, circumscribed plaque. Morphologically, Bowen disease is characterized by the presence of hyperkeratosis, parakeratosis, dyskeratosis, and acanthosis. The keratotic squamous cells are atypical and display hyperchromatism and abnormal mitotic figures. The dermoepidermal basement membrane is intact. Complete surgical removal of the lesion may be curative.