This mutation, namely a 1795GTT insertion, results in BRAF V599Ins. Kinase assays on BRAF V599Ins and BRAF V600E show increased enzymatic activity, increased phosphorylation of MEK, MAPK and RSK and a high transformation rate in the cells compared to wild type BRAF. Thus, BRAF V599Ins, similar to BRAF V600E, is a 'gain of function' mutation, with constitutive activation, which accounts for its role in papillary cancer of the thyroid.