Making a definitive diagnosis of seborrheic keratosis (SK) can be challenging for the naked eye due to its wide variation in clinical features, according to a recent review. Fortunately, most cases of SK exhibit the typical dermoscopic findings of fissures and ridges, hairpin vessels with white halo, comedo-like openings, and milia-like cysts, all of which are helpful to distinguish SK from melanoma, melanocytic nevus, squamous cell carcinoma, basal cell carcinoma (BCC) and other skin tumors. Histopathologically, these dermoscopic characteristics correspond to papillomatous surface of the epidermis, enlarged capillaries of the dermal papillae, pseudohorn cysts in the epidermis opened to the surface of the lesion, and intraepidermal cysts, respectively. Clinicians should bear in mind that the clonal type of SK dermoscopically mimics melanoma and BCC by the presence of globule-like structures, while regressing SK exhibits a granular pattern that is similar to the peppering found in melanoma. Furthermore, milia-like cysts alone are insufficient for a conclusive diagnosis of SK because melanoma in rare cases displays cysts along with other SK-like dermoscopic findings.
Minagawa A. Dermoscopy–pathology relationship in seborrheic keratosis. J Dermatol. 2017;44(5):518-524. doi:10.1111/1346-8138.13657.
This article contains important learning points about seborrheic keratoses. First, there can be wide variations in clinical features. Second, clonal seborrheic keratoses can dermoscopically mimic melanoma and basal cell carcinoma. Regressing seborrheic keratoses can dermoscopically mimic melanoma as well. Finally, milia-like cysts can be seen in cases of melanoma, as well. All of these points emphasize the need for biopsy in cases where the diagnosis of seborrheic keratosis is in doubt.
—Jeffrey M. Weinberg, MD, FAAD
Assistant Clinical Professor of Dermatology, Columbia University College of Physicians and Surgeons, NYC
Director, Clinical Research Center/Dermatopharmacology, St. Luke's-Roosevelt Hospital Center, NYC
Acting Director, Division of Dermatology, Jamaica Hospital Medical Center, NYC
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