Dermoscopic Clues for Diagnosing Melanomas That Resemble Seborrheic Keratosis

Abstract

<p class="first" id="d9664015e523">This observational study reports the dermoscopic examination of 134 cases of melanoma that clinically mimics seborrheic keratosis. </p><div class="section"> <a class="named-anchor" id="ab-doi170004-1"> <!-- named anchor --> </a> <h5 class="section-title" id="d9664015e529">Question</h5> <p id="d9664015e531">What is the dermoscopic appearance of melanomas that clinically simulate seborrheic keratosis? </p> </div><div class="section"> <a class="named-anchor" id="ab-doi170004-2"> <!-- named anchor --> </a> <h5 class="section-title" id="d9664015e534">Findings</h5> <p id="d9664015e536">In this observational study of 134 cases of melanoma, 82% of clinically seborrheic keratosis–like melanomas were correctly detected by dermoscopy, despite the presence of features typically observed in seborrheic keratosis. The presence of the blue-black sign was the most helpful criterion and was independently associated with a correct diagnosis. </p> </div><div class="section"> <a class="named-anchor" id="ab-doi170004-3"> <!-- named anchor --> </a> <h5 class="section-title" id="d9664015e539">Meaning</h5> <p id="d9664015e541">Seborrheic keratosis–like melanomas can be clinically and dermoscopically challenging to detect, but careful dermoscopic examination leads to the recognition and correct diagnosis of melanoma. </p> </div><div class="section"> <a class="named-anchor" id="ab-doi170004-4"> <!-- named anchor --> </a> <h5 class="section-title" id="d9664015e545">Importance</h5> <p id="d9664015e547">Melanomas that clinically mimic seborrheic keratosis (SK) can delay diagnosis and adequate treatment. However, little is known about the value of dermoscopy in recognizing these difficult-to-diagnose melanomas. </p> </div><div class="section"> <a class="named-anchor" id="ab-doi170004-5"> <!-- named anchor --> </a> <h5 class="section-title" id="d9664015e550">Objective</h5> <p id="d9664015e552">To describe the dermoscopic features of SK-like melanomas to understand their clinical morphology. </p> </div><div class="section"> <a class="named-anchor" id="ab-doi170004-6"> <!-- named anchor --> </a> <h5 class="section-title" id="d9664015e555">Design, Setting, and Participants</h5> <p id="d9664015e557">This observational retrospective study used 134 clinical and dermoscopic images of histopathologically proven melanomas in 134 patients treated in 9 skin cancer centers in Spain, France, Italy, and Austria. Without knowledge that the definite diagnosis for all the lesions was melanoma, 2 dermoscopy-trained observers evaluated the clinical descriptions and 48 dermoscopic features (including all melanocytic and nonmelanocytic criteria) of all 134 images and classified each dermoscopically as SK or not SK. The total dermoscopy score and the 7-point checklist score were assessed. Images of the lesions and patient data were collected from July 15, 2013, through July 31, 2014. </p> </div><div class="section"> <a class="named-anchor" id="ab-doi170004-7"> <!-- named anchor --> </a> <h5 class="section-title" id="d9664015e560">Main Outcomes and Measures</h5> <p id="d9664015e562">Frequencies of specific morphologic patterns of (clinically and dermoscopically) SK-like melanomas, patient demographics, and interobserver agreement of criteria were evaluated. </p> </div><div class="section"> <a class="named-anchor" id="ab-doi170004-8"> <!-- named anchor --> </a> <h5 class="section-title" id="d9664015e565">Results</h5> <p id="d9664015e567">Of the 134 cases collected from 72 men and 61 women, all of whom were white and who had a mean (SD) age of 55.6 (17.5) years, 110 (82.1%) revealed dermoscopic features suggestive of melanoma, including pigment network (74 [55.2%]), blue-white veil (72 [53.7%]), globules and dots (68 [50.7%]), pseudopods or streaks (47 [35.1%]), and blue-black sign (43 [32.3%]). The remaining 24 cases (17.9%) were considered likely SKs, even by dermoscopy. Overall, lesions showed a scaly and hyperkeratotic surface (45 [33.6%]), yellowish keratin (42 [31.3%]), comedo-like openings (41 [30.5%]), and milia-like cysts (30 [22.4%]). The entire sample achieved a mean (SD) total dermoscopy score of 4.7 (1.6) and a 7-point checklist score of 4.4 (2.3), while dermoscopically SK-like melanomas achieved a total dermoscopy score of only 4.2 (1.3) and a 7-point checklist score of 2.0 (1.9), both in the range of benignity. The most helpful criteria in correctly diagnosing SK-like melanomas were the presence of blue-white veil, pseudopods or streaks, and pigment network. Multivariate analysis found only the blue-black sign to be significantly associated with a correct diagnosis, while hyperkeratosis and fissures and ridges were independent risk markers of dermoscopically SK-like melanomas. </p> </div><div class="section"> <a class="named-anchor" id="ab-doi170004-9"> <!-- named anchor --> </a> <h5 class="section-title" id="d9664015e570">Conclusions and Relevance</h5> <p id="d9664015e572">Seborrheic keratosis–like melanomas can be dermoscopically challenging, but the presence of the blue-black sign, pigment network, pseudopods or streaks, and/or blue-white veil, despite the presence of other SK features, allows the correct diagnosis of most of the difficult melanoma cases. </p> </div>