By Gary M. White, MD
A "barnacle on the ship of life".
The seborrheic keratosis (SK) is a benign growth on the skin of an adult. It is extremely common and entirely benign.
The SK typically appears as a stuck-on brown, warty, dry plaque. It can however be white or red, greasy or scaly, raised or flat. On occasion, it may be so black as to mimic a melanoma, thus requiring biopsy. A common pattern on the back is multiple linear lesions like raindrops.
Some patients fear being covered with seborrheic keratoses when they get older. They remember how their parents looked and worry they will look the same.
Multiple inflamed keratoses with a lichenoid infiltrate may occur on chronically sun-exposed areas of older patients, particularly women. See multiple lichenoid keratoses.
In one study, the dermatologist could accurately diagnose the SK with over 99% accuracy [Arch Dermatol 2000;136;800]. If there is any question about diagnosis, a shave biopsy should be performed. If the diagnosis is assured, the SK may be ignored as it is entirely benign. Still, many patients desire that their SKs be removed as they are rough, catch on clothing, and are unsightly. The ethics of treating a benign SK free of charge in the group practice setting is discussed here [JAAD 2015;73;518–520].
Cryotherapy is quick and effective in the majority of cases, however, significant postinflammatory hyperpigmentation may occur e.g., in Asians or darker-skinned individuals on the face or below the knee.
Light electrocautery (and curettage if needed) after local anesthesia can provide excellent cosmetic results, perhaps with less risk of pigmentary change.
Raindrops on the back--a common pattern.
SK made a little darker with self-tanning lotion.
Often times the surface keratotic layer flakes off as shown here (and then regrows).
For more pictures of seborrheic keratoses, see SK gallery1 and gallery2.
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