Human papilloma viruses, especially HPV types 6, 11, 16 and 18, often play a part. These are sexually trans-mitted, so the risk of carcinoma of the vulva or penis is greatest in those who have had many sexual partners. Squamous cell carcinoma of the glans penis is especially common in the uncircumcised. Smegma can incite inflammation leading to both phimosis and carcinoma. Exposure to tar also predisposes to scrotal carcinoma. Other predisposing factors are immunosuppression, lichen sclerosus and, possibly, lichen planus. Cancer can also develop from bowenoid papulosisagrowths on the penis that resemble dark seborrhoeic keratoses clinically, and Bowen’s disease histologically. The female equivalent is vulvar intraepithelial neoplasia.
In men, a glistening irregular red moist patch (Fig. 13.39; Bowen’s disease/erythroplasia of Queyrat) develops on an uncircumcised penis, either on the glans or on the inner prepuce.
Maceration may make it look white until evaporation reveals its true colour. It enlarges slowly, and invasion and tumour formation may not occur for years in immunocompetent men. In women, the precursor lesion is often Bowen’s disease presenting as a sharply marginated, very slowly growing, mildly hyperkeratotic or slightly scaling, oddly shaped red patch or plaque that is usually a single lesion on one labia or in the perineum. This may become huge (up to 10 cm diameter). Sometimes cancer of the penis or labia resembles a large wart destroying the underlying tissue. Biopsy confirms the diagnosis.
Eventually the precursor lesions become frankly invasive and capable of metastasizing. Invasive carci-nomas present either as bleeding ulcerated indurated plaques, or as tumorous nodules.
Mohs’ micrographic excision is probably the best treatment for small and minimally invasive carcinomas, but partial penectomy is indicated if the tumour is large. Precursor lesions such as warts, bowenoid papulosis, vulvar intraepithelial neoplasia and Bowen’s disease can be destroyed with laser surgery or cryotherapy. In some patients, topical applications of the cytokine-inducer imiquimod cream or the chemotherapeutic 5-fluorouracil cream can be curative.