A study of Dermoscopic patterns in flat verrucous lesions; clues to differentiate verruca plana from seborrheic keratosis

Background: Seborrheic Keratosis (SK) are the most common benign epidermal lesions, which are raised brown or black papules with a “stuck on” appearance (Mackie, 2004). They may sometimes present with a plane flat verrucous surface which may be clinically confused with verruca plana (VP). Such lesions pose diagnostic challenge to the dermatologists. Since these two have significantly different etiology, treatment and prognosis, differentiation of SK from verruca is necessary. Objective: To study the dermoscopic patterns in plane verrucous lesions and determine its use in differentiating SK from VP. Materials and Methods: Eighteen patients with clinically plane warty lesions were selected. After obtaining consent dermoscopy was performed using a OITEZ e-Scope under white and polarized light with 20x and 200x magnifications. Dermoscopic patterns were observed and histopathological examination was done to confirm the diagnosis. Results: Among the 18 patients, on histopathology 14 patients were having SK and 4 had VP. Among the 14 patients of SK, features found on dermoscopy were; comedo like openings – 12 patients (86%), fissures and ridges – 10 patients (71%), milia like cysts – 4 patients (28%), hair pin vessels – 2 patients(14%), fingerprint pattern – 2 patients (14%) and moth eaten border - 4 patients (28%), sharp demarcation – 10 patients (71%). Among lesions of VP, dotted vessels – 4 patients (100%) and white halo - 3 patients (75%) were seen. Conclusion: Verruca plana being close differential to SK and having different treatment requires appropriate diagnosis. Dermoscopic patterns are characteristiscally specific with no overlapping findings in both the conditions. Thus we suggest the use of noninvasive, quick tool like dermoscopy in differentiating these conditions.