That Skin Growth May Not Be a Wart—It Might Be Seborrheic Keratosis

Benign lesions that don't ever turn into cancer, seborrheic keratoses (or Seb K's for short) can look dangerous. In reality, they are just annoying. The lesions, which are also irreverently called skin barnacles, come in all different shapes and sizes—from large, black growths to barely noticeable, raised areas.

These skin growths have some defining characteristics that will help you spot them. For one, they are classically described as looking like someone took clay or a blob of dirt and stuck it onto the skin. The edge of the skin barnacle 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.

Seborrheic keratoses may look like warts, but they don't contain the human papillomavirus that causes warts. As they develop, some can have a very rough surface with deep pits and fissures, almost like cauliflower being pulled apart.

Some skin barnacles don't have rough surfaces. 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 are actually bits of keratin that develop in a whirling, circular pattern. Sometimes these horn pearls are best seen with a magnifying glass.

For some reason, seborrheic keratoses tend to itch, especially the older you get. Some people will unintentionally manipulate or pick at a seborrheic keratosis and cause it to be further irritated. If it becomes 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.

A dermatologist can usually diagnose a seborrheic keratosis just from its appearance to the naked eye. For good measure, the doctor may shave a piece of it to be examined in the lab to rule out skin cancer. Here are the treatment options:

• Leave any lesions alone: The first and usually the best choice is to leave any skin barnacles alone. They may get larger, but they are not precancerous, so leaving them there for life is not a problem. Seborrheic keratoses are usually removed because they itch, or they interfere with clothing or jewelry, or they are cosmetically unacceptable. That last option is a judgment call. The warty-looking bump on an 80-year-old man's nose may not be as big of a deal as the one on a 40-year-old woman's nose.
• Removal via liquid nitrogen: A small seborrheic keratosis can be frozen off with liquid nitrogen. Liquid nitrogen works by freezing and destroying the cells but leaving the connective tissue foundation intact. The frozen lesion forms a blister as the water is released from the now-dead cells and 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 fewer pigment-producing cells. The scar is usually flat unless you have a tendency to form keloids.

Sometimes seborrheic keratoses can be very difficult to distinguish from melanoma, a form of skin cancer. Especially when they first appear, they can have several of the characteristics of atypical growths. They can have irregular borders and color variation throughout the lesion. So you should not hesitate to see your doctor about any skin rashes or bumps that concern you.