Strikingly, treatment of tumor DNA with uracil-DNA glycosylase (UDG), which is used to digest uracil laden DNA that can result from FFPE-mediated cytosine deamination, was estimated to deplete rare subclonal variants resulting from FFPE artifacts by at least 88% (Fig. 1C, D) (Additional file 2: All UDS-UMI/UDG variants). This evidence concerns the gene UNG and neoplasm.