EGFR and neoplasm: The EGFR status of tumors of patients with advanced stage NSCLC can be evaluated with several biological sources: (i) tissue biopsies (of bronchial or transthoracic origin); (ii) cytological samples (from transbronchial or transthoracic fine needle aspiration; fluid effusions, in particular pleural or cerebrospinal; and bronchoalveolar lavage); (iii) blood samples, mostly from circulating free DNA and sometimes from circulating tumor cells (CTCs); and, more rarely, (iv) surgical specimens [27] (Figure 1).