In fact, two cases with coverage of 4,538X and 4,830X, respectively, had detectable mutations at variant allele frequencies of 0.057 and 9.44% for EGFR p.E746_A750del (exon 19 deletion), suggesting a biological (such as low tumor shedding into circulation) rather than a technical reason for discordance. The gene discussed is EGFR; the disease is neoplasm.