KRAS and neoplasm: ctDNA analysis of pre- and post-operative plasma samples and tumor tissue (n = 42) using PCR-based SafeSeqS assays to identify KRAS mutation (codons 12, 13, and 61) identified RAS mutations in 90.5% of tumor samples and in 62.2% of 37 pre-operative and 37.1% of 35 post-operative plasma samples.