Seborrheic keratosis (SK)–like melanomas are difficult to diagnose dermoscopically, though presence of the blue-black sign, pigment network, pseudopods or streaks, and/or blue-white veil can provide clues, according to a study published in the JAMA Dermatology.1

SK-like melanoma is difficult to diagnose, and the role of dermatoscopy in identifying these lesions is unknown. Many practitioners remove SKs without evaluating the lesion with dermoscopy or sending for pathologic analysis. The goal of this study was to describe dermatoscopic characteristics of SK-like melanomas.

The study included 134 cases of SK-like, histopathologically-proven melanomas that were retrospectively reviewed by 2 dermatoscope-trained observers.

Melanoma features were present in 82.1% of cases, including pigment network (55.2%), blue-white veil (53.7%), globules and dots (50.7%), pseudopods or streaks (35.1%), and the blue-black sign (32.3%). The observers assigned the remaining 17.9% of cases as likely SKs.

A multivariate analysis demonstrated that the blue-black sign was significantly associated with a correct diagnosis (odds ratio [OR], 0.20; 95% CI, 0.001-0.316; P = .006). Hyperkeratosis was an independent risk factor to misclassify SK-like melanoma (OR, 12.05; 95% CI, 2.08-69.86; P = .005).

Pigment network, blue-white veil, irregular globules and dots, pseudopods or streaks, and the blue-black significantly improved SK-like melanoma diagnosis (all P ≤ .03).

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The authors wrote that “this study supports the view that a proportion of melanomas may resemble SK.” Dermoscopic features can help diagnose SK-like melanoma, though histopathologic analysis may still be necessary.

Reference

  1. Carrera C, Segura S, Aguilera P, et al. Dermoscopic clues for diagnosing melanomas that resemble seborrheic keratosis. JAMA Dermatol. 2017 Mar 29. doi: 10.1001/jamadermatol.2017.0129 [Epub ahead of print]