Challenges for New Adopters in Pre-Surgical Margin Assessment by Handheld Reflectance Confocal Microscope of Basal Cell Carcinoma; A Prospective Single-center Study

In vivo reflectance confocal microscopy (RCM) is a useful tool for assessing pre-surgical skin tumor margins when performed by a skilled, experienced user. The technique, however, poses significant challenges to novice users, particularly when a handheld RCM (HRCM) device is used. To evaluate the performance of an HRCM device operated by a novice user to delineate basal cell carcinoma (BCC) margins before Mohs micrographic surgery (MMS). Prospective study of 17 consecutive patients with a BCC in a high-risk facial area (the H zone) in whom tumor margins were assessed by HRCM and dermoscopy before MMS. Predicted surgical defect areas (cm ) were calculated using standardized photographic digital documentation and compared to final defect areas after staged excision. No significant differences were observed between median HRCM-predicted and observed surgical defect areas (2.95 cm [range: 0.83-17.52] versus 2.52 cm [range 0.71-14.42]; P = 0.586). Dermoscopy, by contrast, produced significantly underestimated values (median area of 1.34 cm [0.41-4.64] versus 2.52 cm [range 0.71-14.42]; P < 0.001). Confounders leading to poor agreement between predicted and observed areas were previous treatment (N = 5), a purely infiltrative subtype (N = 1), and abundant sebaceous hyperplasia (N = 1). Even in the hands of a novice user, HRCM is more accurate than dermoscopy for delineating lateral BCCs margins in high-risk areas and performs well at predicting final surgical defects.