This limitation may, however, be minor, because acquired KIT mutations are common in imatinib-resistant GIST reducing the applicability of the primary tumour mutation analysis (Heinrich et al, 2003), and because recent studies show that multiple acquired mutations are often present in imatinib-resistant GIST (Wardelmann et al, 2006; Liegl et al, 2008). This evidence concerns the gene KIT and gastrointestinal stromal tumor.