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Evaluation of verruca plana by in vivo reflectance confocal microscopy and dermoscopy

I N VIVO reflectance confocal microscopy (RCM) is a non-invasive, repetitive imaging tool that provides real-time images at a nearly cellular histological resolution (1). It has been used for the evaluation of several skin diseases, such as Melanoma (2), basal cell carcinoma (3), and psoriasis (4). Dermoscopy is also an in vivo technique, which have become widely used in diagnosis of skin diseases, such as pigmented skin tumors, inflammatory skin diseases, and infectious skin diseases (5). In fact the most dermoscopic features are well correlated with histopathological criteria. Verruca plana (VP) is the intra-epidermal tumor caused by infection of the papilloma virus. The VP lesions are spread by direct or indirect contact and generally occur during childhood and adolescence, but may be seen in patients of all ages. Clinically some skin diseases, such as seborrheic keratosis (SK), syringoma and lichen planus can be very similar to VP and the differential diagnosis between them without histopathological basis is often challenging to dermatologists. Dermatopathology has been developed for more than two centuries and is considered as the ‘gold standard’ in the diagnosis of many skin diseases. However, biopsy is generally invasive, with injuries, pain and scars, which may decrease the compliance of the patients. Clinically, non-invasive methods are urgently required, especially in the diagnosis of lesions in an exposal area. In this study, we recruited 55 cases with typical lesions to further investigate the imaging features using RCM and dermoscopy. Fifty-five patients (33 female and 22 male) with a clinical diagnosis of VP without treatment between 18 and 52 years of age (mean age 32.5 years) were included. The duration of disease of 55 patients was between 3 weeks and 10 years, 20 patients (36.4%) had the disease for less than 1 year and 35 patients (63.6%) for over 1 year. Approximately 34 of the VP patients showed face involvement (72.7%), followed by extremities (21.9%) and trunk involvement (5.5%). All the cases were recruited prospectively from the Dermatology Department of The Third People’s Hospital of Hangzhou. Dermoscopic images were recorded by means of a digital video microscope (Medicam 800HD; FotoFinder Systems GmbH, Birbach, Germany), using a 20and 50-fold magnification. Then, in vivo RCM imaging was performed using a commercially available, near infrared, reflectance mode confocal microscope (Vivascope 1500; Lucid Inc., Rochester, NY, USA), which uses a diode laser at an 830 nm wavelength and a laser power of <20 mW at the tissue level. Because of the low power, no tissue damage occurred. A 930 water-immersion objective lens with a numerical aperture of 0.9 was used with pure water (refractive index = 1.33) as an immersion medium. If images with a spatial resolution of 0.5–1.0 mm in the lateral and 3– 5 mm in the axial dimension, providing insight into cellular structures of the examined specimens in vivo. Usually, an examination depth of 350 lm can be reached, which corresponds to the papillary dermis. Those four patients with typical VP in this study were biopsied. Biopsies of the lesions at