Abstract and Introduction
Background: Although several dermoscopic features of in situ melanoma have been identified, data on confocal features of in situ melanoma are still lacking.
Objectives: To identify reflectance confocal microscopy (RCM) features of in situ melanoma and to develop a diagnostic score combining dermoscopy and RCM.
Methods: In total, 120 in situ melanoma and 213 nevi (test set) were retrospectively analysed to assess the presence of dermoscopic and RCM criteria. Facial and acral lesions were excluded. Spearman's correlation, univariate and multivariate regression models were used to identify features significantly correlated with in situ melanoma diagnosis. Multivariate results on the test set allowed the development of a multistep algorithm, that was tested on a validation set of 100 lesions.
Results: The dermoscopic findings of an atypical network and regression were independent predicting factors for in situ melanoma diagnosis [odds ratio (OR) 3·44, 95% CI (confidence interval) 1·70–6·97 and OR 4·17, 95% CI 1·93–9·00, respectively]. Significant confocal predictors for malignancy were epidermal pagetoid spread (OR 2·83, 95% CI 1·32–6·04) and junctional cytological atypia (OR 3·39, 95% CI 1·38–8·30 if focal, OR 8·44, 95% CI 3·21–22·16 if widespread). A multistep diagnostic algorithm able to predict in situ melanoma with a sensitivity of 92·5% and a specificity of 61% was developed. The validation set confirmed the high diagnostic value (sensitivity 92%, specificity 58%).
Conclusions: An easy and reproducible multistep algorithm for in situ melanoma detection is suggested, that can be routinely used in tertiary centres.
The combined incidence of in situ melanoma and invasive melanoma has been increasing by 2·6% annually over the past decade, with intraepidermal tumours constituting the majority of the burden.[1,2]In situ melanoma is a melanoma that is limited to the epidermis and as such has no associated direct mortality. However, there is an association with an increased risk of developing second primary tumours. Specifically, patients with in situ melanoma are at much higher risk of developing a subsequent primary melanoma, leading dermatologists to recommend regular screening of patients with pigmented lesions. In order for screening to be a successful tool, physicians must be able to diagnose in situ melanoma while avoiding the unnecessary excision of benign lesions.
Dermoscopy is widely used in clinical practice and claimed as the pivotal tool for skin cancer diagnosis. Regarding in situ melanoma diagnosis, dermoscopic features such as an atypical reticular pattern and regression features have been identified[6–11] However, diagnosis of in situ melanoma can be problematic because it is rather difficult to differentiate it from the so–called 'atypical' nevi.
Reflectance confocal microscopy (RCM) improves the diagnostic accuracy in skin cancer detection when combined with dermoscopy even for difficult–to–diagnose inconspicuous lesions.[12–21]
The aims of the current study were: (i) to identify the RCM diagnostic features of in situ melanoma; and (ii) to develop a diagnostic score for in situ melanoma combining dermoscopic and confocal criteria.
The British Journal of Dermatology. 2018;179(1):163-172. © 2018 Blackwell Publishing