Differentiating seborrheic keratosis from skin neoplasm.

The pigmented acanthotic type of lesion may resemble malignant melanoma. When in doubt, a biopsy will usually resolve the question. Seborrheic keratoses may become irritated or inflamed after trauma, biopsy, or exposure to irritants, causing transformation of the basaloid cell type to squamous cells. Such changes may be misinterpreted as diagnostic of basal or squamous epithelioma.