Pigmented Basal Cell Carcinoma on Buttocks of a 60-Year-Old Woman

A 60-year-old woman was referred by her gynecologist because of a lesion on the buttocks of which the patient first became aware when she noticed blood on her underwear. Physical examination revealed an irregularly pigmented and slightly eroded asymmetric plaque (A and B). Examination with a magnifier highlighted a slightly rolled border, from which a shave biopsy was performed.

Pathology studies demonstrated features consistent with pigmented basal cell carcinoma, including islands of basaloid cells in the dermis with palisading of basaloma cells at the periphery. Melanin pigment was present within the basaloid islands.

Basal cell carcinoma usually, but not exclusively, develops on sun-exposed skin. The most common type is the nodulo-ulcerative basal cell carcinoma, which begins as a pearly or translucent papule with overlying telangiectases and a central umbilication or early ulceration. The lesion gradually enlarges and may appear as a centrally ulcerated plaque with a rolled, pearly border.

The superficial basal cell carcinoma appears as a thin, scaling, red plaque with a pearly, rolled periphery; it usually arises on the trunk. The morphea-like basal cell carcinoma resembles a scar and manifests as a depressed, skin-colored to yellow papule or plaque with poorly defined borders. Nodulo-ulcerative and superficial carcinomas may display brown pigmentation as a result of melanocytes within the tumors.

Pigmented basal cell carcinomas may be confused clinically with seborrheic keratoses, benign melanocytic nevi, pigmented Bowen's disease, and malignant melanoma. They are most commonly treated by surgical excision or by curettage and desiccation. Cryotherapy and radiation therapy are used less commonly. The choice of treatment depends on factors such as the age and health of the patient as well as the type, size, and location of the lesion. For example, tumors on the nose and ear have a high rate of recurrence, and excision or Mohs' microscopically controlled surgery (in which margins are checked at the time of the procedure) are therefore preferable to curettage and desiccation.

Curettage and desiccation are generally adequate treatments for superficial basal cell carcinomas on the trunk. Morphea-like carcinomas have poorly defined margins and often affect cosmetically vulnerable sites, such as the central face, making Mohs' surgery the treatment of choice; it affords both tissue conservation and optimal margin analysis. A discrete nodulo-ulcerative papule on the lateral cheeks or forehead in an elderly patient poses a small risk of recurrence and is amenable to curettage and desiccation. The lesion described in the case pictured here was treated by standard surgical excision.