Breslow density is a novel prognostic feature in cutaneous malignant melanoma.

Aims In 1970, Breslow described his eponymously named thickness measurement. No-one has sought to enhance Breslow thickness (BT). This purpose of this study was to demonstrate proof of concept that the density of melanoma cells at the position where Breslow thickness is measured is a morphological prognostic biomarker, which we name Breslow density (BD). The hypothesis was that BD has prognostic value for overall survival (OS) and is independent of BT. Methods and results We analysed 100 cutaneous melanomas and followed REMARK guidelines. BD was the estimated percentage dermal area occupied by melanoma cells in a specified location. BT and BD had a strong correlation (p = 2.1 x 10-11) but despite this they were independent prognostic factors for OS in Cox regression (BD: HR 1.03, p=0.001849 and BT: HR 1.09, p=0.000146). This was corroborated by an independent effect on melanoma specific survival. We assessed whether BT and BD could be combined into a Breslow score. A prognostic index based on Cox regression coefficients was used and this showed a marginal improvement in predicted 5-year survival compared to BT alone (are under curve 94.8% v 96.7%). Conclusions We show proof of concept that BD represents a novel morphological prognostic biomarker that is independent of BT and that there is potential to combine these into a Breslow score. Larger studies are needed to validate BD, but the simplicity of this biomarker makes it a strong candidate for translation to clinical practice. This article is protected by copyright. All rights reserved.