Seborrheic keratoses.

Seborrheic keratoses are benign tumors of the epidermis that commonly appear during middle age. They are pigmented verrucous papules with a characteristic "stuck on" appearance. The tumors enlarge and become more deeply pigmented with age. The precise etiology is unknown. Differential diagnosis includes malignant melanoma and pigmented basal cell carcinoma. Biopsy should be performed if the diagnosis is in doubt. Treatment, when indicated, includes curettage, shave excision, freezing with liquid nitrogen or the use of trichloroacetic acid.