A seborrheic keratosis (also known as "seborrheic verruca," and "senile wart") is a noncancerous benign skin growth that originates in keratinocytes. Like liver spots, seborrheic keratoses are seen more often as people age. In fact, they are sometimes humorously referred to as the "barnacles of old 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 (1.0 in) across. They can resemble warts, though they have no viral origins. They can also resemble melanoma skin cancer, 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.
The causes of seborrheic keratosis are unclear. Because seborrheic keratoses are common on sun exposed areas such as the back, arms, face, and neck, ultraviolet light may play a role, as may genetics. However, they are also found on skin that has not been exposed to the sun. A mutation of a gene coding for a growth factor receptor, has been associated with seborrheic keratosis.
Although no direct cause-effect relationship between physiological stress and tumors in general has been medically established, medically, stress is recognized as a potential factor in the exacerbation of preexisting tumors, including those which are benign. Therefore, physiological stress has the potential to worsen a preexisting condition such as seborrheic keratosis Seborrheic keratosis also may be one of the many symptoms of gastrointestinal malignancies
Visual diagnosis is made by the "stuck on" appearance, horny pearls or cysts embedded in the structure. Darkly pigmented lesions can be hard to distinguish from nodular melanomas. If in doubt, a skin biopsy should be performed. Thin seborrheic keratoses on facial skin can be very difficult to differentiate from lentigo maligna even with dermatoscopy.