TY - JOUR T1 - Intratumorous heterogeneity for RAS mutations in a treatment-naïve colorectal tumour JF - Journal of Clinical Pathology JO - J Clin Pathol SP - 720 LP - 723 DO - 10.1136/jclinpath-2017-204327 VL - 70 IS - 8 AU - Sebastian Lunke AU - Belinda Lee AU - Sevastjan Kranz AU - Peter Gibbs AU - Paul Waring AU - Michael Christie Y1 - 2017/08/01 UR - http://jcp.bmj.com/content/70/8/720.abstract N2 - Activating mutations in KRAS and NRAS genes in patients with colorectal cancer (CRC) are associated with a lack of response to treatment with anti-epidermal growth factor receptor (EGFR) therapies. Mutations in these genes are thought to be mutually exclusive, however reports have described CRCs with two activating rat sarcoma (RAS) mutations. This has fuelled discussion about whether these mutations are the result of intratumorous heterogeneity, or if they are co-occurring in the same cancer cell clone. We present a case of a colorectal tumour with three RAS mutations detected during routine diagnostic testing. Further detailed analysis with laser capture microdissection and next generation sequencing excluded the possibility of all three mutations being present in the same clone, presenting the highest resolution evidence of intratumorous heterogeneity of RAS mutations to date. ER -