Successful treatment of solar lentigines by brief gentle cryosurgery using a Kryomed®device

Sir, Solar lentigines are common benign melanocytic proliferations representing a cosmetic problem in older Caucasian individuals. Melanocytes are the most vulnerable skin cells to cold and are destroyed at −4 to −7 °C.1 Indeed, Zouboulis et al. have shown that liquid nitrogen produces excellent results in patients with large lentigo lesions.2 Stern et al. have reported that liquid nitrogen cryosurgery was superior to argon or CO2 laser therapy in the treatment of solar lentigines.3 We therefore evaluated the effectiveness of two brief gentle cryosurgery regimens in 20 female Caucasian patients with solar lentigines on the back of the hands (diameter ≥ 3 mm). A randomized, controlled, prospective trial compared single treatments of 5 s (group A; n = 10, aged 66·9 ± 10·3 years) and 10 s (group B; n = 10, 61·8 ± 10·4 years) with a contact cryosurgical unit using a Peltier thermoelectric element achieving a skin surface temperature of −32 °C (Kryomed®; MediUm‐TECH, Berlin, Germany) (Fig. 1). The therapeutic result was evaluated after 1 and 6 months by visual inspection. In addition, a chromametric assessment of the colour of the lesion was performed using a Minolta CR−300 Chroma Meter® (Osaka, Japan).4 The chromameter was set in the L*a*b* colour space. The equation C* = [a*2 + b*2]1/2 describes the quality of colour. L* represents the ‘value’ of the colour, and in comparisons, positive values indicate lighter and negative darker colours. The equation E* = [L*2 + a*2 + b*2]1/2 takes into consideration both the quality (C*) and the value (L*) of colour and allows an overall comparison of colours. Measurements of skin lesions at different time points were made comparable by concomitant evaluation of normal skin of the same anatomical site.5