Recognizing the benefits and pitfalls of reflectance confocal microscopy in melanoma diagnosis

The incidence of melanoma has been on the rise for the last several decades, with a current US lifetime risk of developing melanoma estimated as 1 in every 60 individuals [1]. The key to preventing death from melanoma is the early detection of this cancer, at a stage where surgical excision is curative. However, in attempt to diagnose melanoma early, physicians are also removing many benign lesions, most of these being melanocytic nevi. The pursuit to improve our clinical sensitivity for melanoma diagnosis, while minimizing unnecessary skin biopsies, has led to the development of skin imaging techniques. Among recent non-invasive imaging modalities, reflectance confocal microscopy (RCM) stands out as particularly promising since it offers bedside imaging at cellular-level resolution. Stevenson and coauthors [2] have reported in Dermatology Practical & Conceptual on a systematic review of the diagnostic accuracy of RCM for melanoma diagnosis. They have identified five publications, including a total of about 900 lesions, a third of which were melanomas; most of these lesions were reportedly equivocal for diagnosis, clinically and dermatoscopically. Based on these studies, the pooled sensitivity for melanoma diagnosis using RCM is 93% (range 91%-97%) and specificity is 76% (range 68%-86%). While the study by Stevenson et al [2] did not address the exact contribution of RCM as an add-on test to dermatoscopy, the aforementioned data suggests that RCM can indeed increase diagnostic accuracy beyond clinical and dermatoscopic examination. To simulate the added contribution of RCM to dermatoscopy, Stevenson et al [2] took a hypothetical case of 1000 dermatoscopically equivocal skin lesions, and based on the previously reported benign to malignant ratio of 4:1 for experts’ diagnosis of melanoma [3], they assume a ratio of 800 benign lesions to 200 melanomas. They estimate that RCM will prevent the unnecessary excision of 608 benign lesions that would be diagnosed as benign based on RCM, reflecting the specificity of 76%. If we were to formulate the best indications for using RCM as an add-on test to dermatoscopy, we would need to better point-out which lesions are included in this group of 608 benign lesions that are dermatoscopically equivocal, but RCM negative. In this editorial, we can only attest to our own impression and experience, as well as some literature reports, that this group of lesions could encompass the following examples: Recognizing the benefits and pitfalls of reflectance confocal microscopy in melanoma diagnosis