Its paralog PTPRK was identified as a candidate driver gene in mouse intestinal tumorigenesis by insertional mutagenesis (March et al., 2011; Starr et al., 2009) and was more recently identified as a gene fusion partner with the oncogene RSPO3 in a subset of human colorectal cancers (Seshagiri et al., 2012). The gene discussed is RSPO3; the disease is colorectal cancer.