Seborrheic keratosis

A seborrheic keratosis, also known as seborrheic verruca or a senile wart,) is a benign skin tumor that originates from keratinocytes. Like liver spots, seborrheic keratoses are seen more often as people age.

The lesions appear in various colors, from light tan to black. They are round or oval, feel flat or slightly elevated, like the scab from a healing wound, and range in size from very small to more than 2.5 centimetres (1 in) across. They can often come in association with other skin conditions, including basal cell carcinoma, as a collision tumor or by means of tumor progression phenomena. At clinical examination the differential diagnosis include, warts (though they have no viral origins) and melanoma (though they are unrelated to melanoma). Because only the top layers of the epidermis are involved, seborrheic keratoses are often described as having a "pasted on" appearance. Some dermatologists refer to seborrheic keratoses as "seborrheic warts"; these lesions, however, are usually not associated with HPV, and therefore such nomenclature is discouraged.