KRAS and squamous cell carcinoma: We also show it is possible to detect pathogenic mutations in ctDNA: While no EGFR mutations were detected in the 12 patients with lung cancer, a number of pathogenic variants were identified in oncogenic kinase genes such as KRAS and in tumour suppressor genes such as TP53 or PTEN. In particular, we revealed pathogenic TP53 mutations in ctDNA from all three squamous cell carcinoma patients, which has been shown to be the most commonly mutated gene in squamous lung cancer, as well as mutations in CDKN2A and PTEN [22].