EGFR and neoplasm: Section 2 discusses the influence of CTC count on chemotherapeutic efficiency. Section 3 describes the potential of CTC analysis to improve therapeutic prognosis mainly in terms of programmed cell death protein ligand 1 (PD-L1) expression and epidermal growth factor receptor (EGFR) genotyping. Section 4 is focused on the mechanisms supporting the spread of CTCs, such as tumour-associated and -infiltrating cells, epithelial–mesenchymal transition (EMT), and cellular migration, and discusses the ability of natural agents to suppress them.