The 'St. Tropez' sign; a new dermoscopic feature of seborrhoeic keratoses?

Abstract

Conflict of interest: none declared. Dermoscopy is a noninvasive technique to assist in the in vivo diagnosis of pigmented skin lesions, and may improve preoperative diagnostic accuracy by up to 30%1 while giving a diagnostic sensitivity as high as 89%.2 Seborrhoeic keratoses (SK) are the commonest nonmelanocytic lesions that cause diagnostic difficulty clinically, but specific dermoscopic features can help establish the diagnosis. We present a new dermoscopic sign of SK. Three months after a foreign holiday, a 54‐year‐old woman noted change in the colour of a lesion on her left lower leg that had been present for at least 3 years. There had been no change in size or shape of the lesion. She had Fitzpatrick type I skin, and the lesion itself was a well‐demarcated, rough‐surfaced, small plaque with patchy orange‐brown pigmentation in small circles and streaks (Fig. 1a; pictures taken with Nikon Coolpix 995). Dermoscopic images (Heine Delta 20 with photoadaptor) revealed a bland background with numerous small globular elements surrounded by varying amounts of pigment giving an almost alveolar appearance Fig. 1(b).