The sometimes rapidly changing growth of a seborrheic keratosis can fool people into thinking they have a melanoma.
But not all seborrheic keratoses grow quickly.
And yes, these benign skin barnacles can look just like a melanoma (and vice versa!), and they can also strongly resemble a dysplastic nevus (atypical mole).
Growth Rate of a Seborrheic Keratosis
“There are different types of seborrheic keratoses — can be flat, thick, small (1-2 mm), or reaching the more typical size of a thumb nail – about 1 cm – in a short time,” explains Sharyn Laughlin, MD, board certified dermatologist and co-founder of the DermaEnvy Skincare ™ line of sun protection products and medical director of Laserderm, a pioneering laser skin surgery clinic in Ottawa, Ontario, Canada.
“They can be white, black or brown; smooth (adenoid type) or very rough (verrucous),” continues Dr. Laughlin.
“They come in crops, sometimes grow quickly with hormonal changes, and are not limited to sun exposed areas since they are not UVR induced.
“They come on with advancing age. It does not matter what it looks like and how fast it has grown, the dermatologist can usually tell the difference after clinical and dermatoscopic examination.”
A dermatoscope is a handheld lens that allows a dermatologist to view intricate details, under magnification, of the lesion of interest.
People as young as 40 can begin developing seborrheic keratoses, and may develop hundreds just on their back.
In isolation they can strongly resemble a mole, but when they’re in highly clustered numbers, they often look as though they’ve been splattered on the skin.
Dr. Laughlin says, “In cases of doubt, excision and pathologic exam will solve the puzzle.”
A seborrheic keratosis that has looked the same for a very long time can suddenly start changing in appearance.
This does not mean cancer if it’s only the barnacle that’s changing, but you should get it checked anyways to make sure there’s not a melanoma springing up among the melanocytes next to the barnacle.
In other words, a melanoma and a seborrheic keratosis can, by chance, share real estate.