Reflectance confocal microscopy (RCM)-based skin cancer diagnosis requires proficiency.
To identify a shortlist of key RCM features of skin cancers and test their diagnostic utility.
We identified key RCM features through consensus among six experts using a modified-Delphi method. To test diagnostic utility of these RCM key-features, ten novice RCM readers evaluated a subset of 100 RCM cases from a retrospective dataset of benign and malignant skin neoplasms.
The experts identified 18 RCM features as highly valuable for skin cancer diagnosis, from 56 features reported in the literature. Based on consensus definitions, these RCM features were further clustered into two melanoma-specific key-features - 'atypical cells' and 'dermal-epidermal junction disarray', one basal cell carcinoma (BCC)-specific key-feature - 'basaloid cords/islands', and one squamous cell carcinoma (SCC)-specific key-feature - 'keratinocyte disarray'. The novice reading study showed that the presence of at least one of the four key-feature was associated with an overall sensitivity for skin cancer diagnosis of 91% - with sensitivity for melanoma-93%, BCC-92% and SCC-77%; and an overall specificity of 57%.
A consensus terminology shortlist, identifying the four RCM key-features for skin cancer diagnosis, may facilitate dissemination of RCM to novice users.
Delphi consensus method; Reflectance confocal microscopy; basal cell carcinoma; diagnostic criteria; melanoma; nevi; squamous cell carcinoma