Bownen's disease may occur in the genital region in both men and women, generally those older than 35 years of age. In men it mainly involves the shaft of the penis and the scrotum.
Grossly, it appears as a solitary, thickened, gray-white, opaque plaque with shallow ulceration and crusting.
Microscopically, there is marked epidermal proliferation with numerous mitosis, some atypical. There is complete loss of normal surface maturation but the basement membrane is intact and there is no invasion of underlying stroma. Transition to invasive squamous cell carcinoma is estimated to occur in about 10% of cases; there is a possible association with visceral malignancies (about one-third of patients).