Contrary to the findings of Bai et al. that tumor EGFR mutation status changed after chemotherapy [132], the experience with several biomarkers to date (including with EGFR mutation status) suggests that formalin-fixed paraffin-embedded (FFPE) archival tissues from initial diagnostic biopsies may be a very adequate source of tissue for biomarker assessment, even if the patient has undergone chemotherapy between tissue acquisition and administration of the targeted therapy [53,72-74,77,78,80,81]. The gene discussed is EGFR; the disease is neoplasm.