Seborrheic Keratosis

Seborrheic keratoses are the most common neoplasms in elderly persons and affect up to 60% of this population. Risk factors for these lesions are thought to include genetic predisposition, age, and sun exposure.^1,2

The hallmark feature of seborrheic keratoses is their pasted-on appearance; the lesions can often be peeled off with the fingers. Macular seborrheic keratoses are round or oval and flat (A). The surface of seborrheic keratoses may be flat, velvety, smooth, or verrucous (B). The lesions are usually brown or yellow-white (C); however, they may be red, gray, wax-colored, yellowish, black, or white.

Seborrheic keratoses start as small lesions but can grow to more than 1 cm or (rarely) larger. They can appear on any part of the body but are most commonly found on the torso. They are not usually accompanied by inflammation or erythema. However, irritation can induce swelling and sometimes bleeding, oozing, and crusting, as well as a darkening of the pigment as a result of inflammation. Seborrheic keratoses may resemble warts, actinic keratoses, melanoma, or inflammatory dermatosis that manifests with scaly or verrucous papules.

Seborrheic keratoses are less common in black persons than in whites. However, a variant of seborrheic keratosis--dermatosis papulosa nigra--sometimes develops in black persons and those of Asian and Hispanic descent. These lesions consist of numerous pedunculated growths that primarily affect the face, neck, and upper chest (D). They appear at an earlier age than seborrheic keratoses.

Treatment is usually not necessary unless the lesions are irritated. Treatment options include cryotherapy with dry ice, liquid nitrogen,³ electrodesiccation with or without curettage, curettage alone, shave biopsy or excision with a scalpel or laser, and dermabrasion surgery. Biopsy is indicated if the diagnosis is ambiguous.

The sign of Leser-Trélat refers to the eruption of innumerable widespread seborrheic keratoses that is thought to indicate internal malignancy. The most commonly reported neoplasm is adenocarcinoma, especially of the GI tract. Seborrheic keratoses can also erupt after an exacerbation of inflammatory dermatitis, such as a flare of eczema or a severe sunburn.