EGFR and lung cancer: In this review, we present a brief overview of clinical perspectives concerning and opportunities for the use of liquid biopsy in lung cancer, focusing specifically on the following: identification of actionable mutations, such as sensitizing (19 del and L858R) and resistant (T790M) EGFR mutations; the significance and uniqueness of the two most popular circulating biomarkers, i.e., CTCs and ctDNA; and the detection methods for each biomarker and the current limitations of these methods.