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Seborrheic Keratosis or Melanoma? Using Dermoscopy to Differentiate

Melanomas can have clinically similar features to seborrheic keratosis (SK), and a mistaken diagnosis can lead to treatment delays. Melanomas and SK alike can have scaly surface, milia-like cysts, and comedo-like openings, among other clinical features. A recent study sought to describe the dermoscopic features of a large series of retrospectively collected and histopathologically diagnosed melanomas for which the clinical differential diagnosis included SK. A secondary goal was to note the main dermoscopic features that have led clinicians to misinterpret melanomas as SKs.

Nine skin cancer centers from Spain contributed clinical and dermoscopic images of pathologically proven melanomas, where SK was listed in the clinical differential diagnosis. Each lesion was evaluated by 2 independent, dermoscopy trained observers. The observers evaluated clinical descriptions and 48 dermoscopic features. One result of this study was that the addition of dermoscopy resulted in the correct diagnosis of melanoma in more than 80% of clinically SK-like melanomas. Also, rather than using dermascopic algorithms (which in this study would have resulted in missed melanoma 50% of the time), dermoscopists can better distinguish benign from malignant lesions using a global image. In addition to the more commonly known melanocytic criteria, the blue-black sign, that is, the presence of blue and black in a hyperpigmented tumor, was associated with SK-like melanomas. Other important features that indicated a SK-like melanoma included pigment network, pseudopods or streaks, and/or blue-white veil, despite the presence of other SK features.

The authors acknowledge that finding a melanoma masquerading as a SK is challenging when a person has multiple SK. However they note that all lesions of patients with numerous SKs should be assessed dermoscopically to increase the possibility of detecting the odd SK-like melanoma.

 

Byline: Martha L. Sikes, MS, RPh, PA-C

Posted: July 20, 2017

Source: JAMA Network
Adapted from the original article.

[Image: Shutterstock]