The present disclosure provides a multiplexed amplification reaction kit for identifying a subject suffering from a malignancy sensitive to treatment with an inhibitor of the Wnt signaling pathway, comprising a primer pair capable of amplifying a PTPRK(e13)-RSPO3(e2) R-Spondin gene-fusion. Also disclosed is a method of identifying sensitivity to an inhibitor of Wnt signaling in a subject suffering from a malignancy, comprising detecting the PTPRK(e13)-RSPO3(e2) R-Spondin gene-fusion with a primer pair.