Barnacles on the ship of life

Over the next few months, we’ll take a closer look at a few of the most common spots that pop up on our skin. Today’s article is about the most common new growth that develops after the age of 40 – the “seborrheic keratosis” or SK for short.

SK’s are benign, which means that they are not cancerous. Still, they are probably THE growth that patients ask me about most frequently. It is understandable that SK’s generate worry because they exhibit many of the features that we teach people to fear. SK’s grow and sometimes itch. If scratched or traumatized, they can hurt or bleed. They can be brown or black. Such spots often cause alarm.

Changing brown or black growths should be examined by a dermatologist to rule out melanoma. The most common differences between SK’s and melanomas are fairly easy to list but can be hard to apply without practice. And because the stakes for misdiagnosing one’s self are so high (death), having a dermatologist look at spots with you is completely justified. Some patients feel silly coming in for something that turns out to be “nothing” but getting checked is smart. Self-diagnosis is not advised, especially not initially. But, with time, patients can often identify most SK’s confidently using these rules:

SK’s have a few reasonably consistent features: they are usually rough or waxy in texture. They are almost always “stuck-on” in appearance similar to a barnacle on a ship. SK’s often feel as if you can get a fingernail underneath the edge and just pop them off (and some patients can and do!). Waxy SK’s are not particularly rough whereas the rough SK’s are often “warty” in appearance.

Other features of SK’s are less consistent. SK’s are often tan or brown, but they can be black, pink, multicolored or even white. On the feet and ankles, white SK’s are called “stucco keratoses and look as if the ankles and feet were spackled with stucco. Seborrheic keratoses range in size from pinpoint to as big as an oyster shell. Given these variations, color and size are not helpful diagnostic features. They often get thicker and bigger with time, so growth isn’t a helpful differentiator either.

What do you do once you’ve confirmed that a growth is “only” an SK? Seborrheic keratoses are easily treatable and can often be frozen away with liquid nitrogen or curetted away with ease. Insurance unfortunately only considers it medically necessary to treat SK’s that are bleeding, irritated, painful, getting rubbed on by clothing or otherwise symptomatic. “Cosmetic” SK removal is available at most dermatology clinics for a cosmetic fee.

Small SK’s can usually be removed with minimal residual blemish, but larger SK’s may leave a lighter-colored area or subtle scar after removal. In one U.S. study, the average American over the age of 40 developed one new SK per year with the average 65-yearold exhibiting 33 SK’s upon a thorough counting. Given how pleasingly SK’s can be removed when they are still small, a “debarnacling” every year or two is a reasonable choice for most individuals.

Given that skin cancer is more than ten times more common than any other cancer, it pays to familiarize yourself with the appearances of skin cancer and its mimics (Google Images is a great tool for this purpose). For patients with concerning spots, a family history of skin cancer or risk factors such as a history of sun damage or tanning bed use, a visit with a dermatologist is highly recommended.