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A seborrheic keratosis (also known as "Seborrheic verruca," and "Senile wart"^{[1]:767[2]:637}) is a noncancerous benign skin growth that originates in keratinocytes. Like liver spots, seborrheic keratoses are seen more often as people age.^[3] In fact they are sometimes humorously referred to as the "barnacles of old age". [1]

They 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 (1.0 in) across.^[4] They can resemble warts,^[3] though they have no viral origins. They can also resemble melanoma skin cancer, though they are unrelated to melanoma as well. 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 should be discouraged.

See here>>>http://en.wikipedia.org/wiki/Seborrheic_keratosis