This study was registered at the German Clinical Trial Register (DRKS-Study-ID: DRKS00013570; https://www.drks.de/drks_web/).

This study provides evidence for the existence of a subgroup of slow-growing melanomas, which may explain the increase in the incidence of thin melanoma, despite stable rates of thick melanoma and melanoma-associated mortality.

The data collected provide a new knowledge regarding the clinical and dermoscopy features of pigmented scalp tumours.

We identified RCM criteria for diagnosis of LPLK that correlate well with histopathological findings and that allow differentiation of LPLK from skin cancer.

Reference1 Cheng ST, Ke CL, Lee CH et al. Rainbow pattern in Kaposi's sarcoma under polarized dermoscopy: a dermoscopic pathological study. Br J Dermatol 2009; 160:801-9.

Background: The ‘gold standard’ for the diagnosis of melanocytic lesions is dermatopathology. Although most of the diagnostic criteria are clearly defined, the interpretation of histopathology slides may be subject to interobserver variability. Objectives: The aim of this study was to determine the variability among dermatopathologists in the interpretation of clinically difficult melanocytic lesions. Methods: This study used the database of MelaFind®, a computer-vision system for the diagnosis of melanoma. All lesions were surgically removed and sent for independent evaluation by four dermatopathologists. Agreement was calculated using kappa statistics. Results: A total of 1,249 pigmented melanocytic lesions were included. There was a substantial agreement among expert dermatopathologists: two-category kappa was 0.80 (melanoma vs. non-melanoma) and three-category kappa was 0.62 (malignant vs. borderline vs. benign melanocytic lesions). The agreement was significantly greater for patients ≥40 years (three-category kappa = 0.67) than for younger patients (kappa = 0.49). In addition, the agreement was significantly lower for patients with atypical mole syndrome (AMS) (kappa = 0.31) than for patients without AMS (kappa = 0.76). Limitations: The data were limited by the inclusion/exclusion criteria of the MelaFind® study. This might represent a selection bias. The agreement was evaluated using kappa statistics. This is a standard method for evaluating agreement among pathologists, but might be considered controversial by some statisticians. Conclusions: Expert dermatopathologists have a high level of agreement when diagnosing clinically difficult melanocytic lesions. However, even among expert dermatopathologists, the current ‘gold standard’ is not perfect. Our results indicate that lesions from younger patients and patients with AMS may be more problematic for the dermatopathologists, suggesting that improved diagnostic criteria are needed for such patients.

These pilot data suggest that dermoscopic pattern may serve as a more robust and specific marker of melanoma risk than clinical naevus phenotype.

No abstract