Analysis of minor variants of secondary KIT mutations in GISTs prior to imatinib therapy. Shown are the mean allele frequency (± the standard deviation) and mean coverage (± the standard deviation) at the positions of the mutations p.V654A (exon 13), p.N680K (exon 14), p.D820E (exon 17) and p.N822Y (exon 17). At each mutation position the results are shown for each of the three panels used: the GS Junior panel, the Qiagen panel and the AmpliSeq panel. The different coloured graphs illustrate the results of primary GISTs (FFPE) with (white) and without (grey) emerging secondary KIT mutations in the recurrent tumours and of GISTs (fresh-frozen) with unknown emerging secondary KIT mutations (dark grey). All measured allele frequencies are below the determined limit of detection (see corresponding Table 4).