Dermatological Services - Seborrheic Keratosis
Seborrheic keratoses are common growths that develop with aging of the skin. Below are some of the characteristics.
Stuck on - They are classically described as looking like someone took clay or a blob of dirt and "stuck" it on the skin. The edge of the seborrheic keratosis is not attached to the underlying skin making it appear that it could be removed by picking it off with your fingernail. This is because seborrheic keratoses arise from the epidermis, or top layer of skin. They don't extend deep into the skin like warts. What you see is what you get.
Warty surface - Seborrheic keratoses may look like warts but they don't contain human papilloma viruses that cause warts. As they develop some can have a very rough surface with deep pits and fissures almost like cauliflower being pulled apart.
Smooth surface with horn pearls - Some seborrheic keratoses don't have a rough surface. If they are smooth, they contain tiny bumps that look like seeds that are lighter or darker than the surrounding tissue. These are called horn pearls and they are actually bits of keratin that develop in a whirling, circular pattern. Sometimes these horn pearls are best seen with a magnifying glass.
Itching - For some reason seborrheic keratoses tend to itch especially the older we get. Some people will unintentionally manipulate or "pick at" a seborrheic keratosis and cause it to be further irritated. If irritated enough, the skin around it can become red and the seborrheic keratosis itself can bleed. This can be alarming to savvy skin-watchers who know that a doctor should see any lesion that bleeds.
What can be done about Seborrheic Keratosis?
The first and usually the best choice is to leave them alone. They may get larger, but they are not precancerous so leaving them there for the life of your skin is not a problem. Seborrheic keratoses are usually removed because they itch, they interfere with clothing or jewelry, or they are cosmetically unacceptable.
Removing Seborrheic Keratosis
If you decide to have a seborrheic keratosis removed, there are several ways to do this.
- Liquid Nitrogen - A small seborrheic keratosis can be frozen with liquid nitrogen. Liquid nitrogen works by freezing and destroying the cells but leaving the connective tissue foundation intact. The lesion frozen forms a blister as the water is released from the now-dead cells then crusts over as that water dries. When the crust falls off after several days, the skin underneath has begun to repair itself. Liquid nitrogen can leave a scar as the repaired skin may have more or less pigment producing cells. The scar is usually flat though unless you have a tendency to form keloids.
- Shave - Another way seborrheic keratoses can be removed is to shave them off. Because their attachment to the underlying skin covers less area than the lesion itself, shaving can be a viable option. Seborrheic Keratoses are shaved off with a flexible razor blade going just deep enough to get only the seborrheic keratosis cells and leave normal skin. Shaving too much normal skin off can leave a divot in the skin as a scar. After the lesion is shaved, a chemical agent such as aluminum chloride or silver nitrate is applied to the wound to stop any small surface bleeding. Silver nitrate is a dark brown color and the resulting wound after the shave is dark brown. This color will usually go away after the skin repairs but some of that pigment can remain. For this reason, silver nitrate is usually not used on the face.
Sometimes seborrheic keratoses can be very difficult to distinguish from melanoma. Especially when they first appear, they can have several of the characteristics of atypical growths. They can have an irregular border and color variation throughout the lesion. You should always have the lesion evaluated by a professional if there is any suspicion that the lesion can be cancerous.