The in-frame deletion in exon 19 (19del; 49–72%) and one nucleotide substitution within codon 858 of exon 21 (L858R; 28–43%) are two predominant epidermal growth factor receptor (EGFR) alterations in non-small cell lung cancer (NSCLC), called “common mutations” or “classic mutations” (Wang and Li, 2019). The gene discussed is EGFR; the disease is non-small cell lung carcinoma.