DNA was extracted from 116 FFPE primary melanoma tumors, sampled horizontally at the advancing edge of the tumor, in the vertical growth phase, using a 0.8 mm × 2 mm core biopsy needle and haematoxylin and eosin stained slides as a guide. The intent was to choose tissue representative of the deepest part of the tumor but which was sufficiently surrounded by tumor that the sample contained minimal normal stroma and inflammatory cell infiltrate. Horizontal sections of cores were taken during development of the methodology to ensure the technique allowed minimal sampling of normal tissue as described previously (Conway et al.,2009). DNA extraction from cores was carried out using the QIAamp DNA Mini kit (Qiagen, Sussex, UK) (Conway et al.,2009).