Cutaneous squamous cell carcinoma in situ (SCCis), also known as Bowen disease, is defined histopathologically by malignant keratinocytes that involve the full thickness of the epidermis. This common malignancy is primarily seen in older adults and most frequently occurs on sun-exposed skin. The development of SCCis has also been associated with immunosuppression, chronic lymphocytic leukemia, radiation exposure, arsenic ingestion, and human papillomavirus (HPV). There is no sex predilection. It is frequently seen accompanying other stigmata of chronic sun damage, such as actinic keratoses, solar lentigines, and other keratinocytic carcinomas. If left untreated, SCCis can evolve into invasive SCC.

Erythroplasia of Queyrat refers specifically to SCCis of the glans penis and prepuce, most commonly seen in uncircumcised individuals. It is typically a red, moist, smooth or eroded plaque.

Bowenoid papulosis refers to a high-risk HPV infection (ie, HPV strains 16 and 18) with histologic features of SCCis, usually in the genital or perianal area. Periungual SCCis is also linked to high-risk HPV infection.

Arsenic-induced SCCis can be multifocal and most commonly affects acral surfaces (see arsenical keratosis).

Related topic: Cutaneous squamous cell carcinoma