Exon 20 (ex20) in-frame insertions or duplications (ins/dup) in epidermal growth factor receptor (EGFR) and its analog erb-b2 receptor tyrosine kinase 2 (ERBB2) are each detected in 1.5% of non–small cell lung cancer (NSCLC). The gene discussed is ERBB2; the disease is non-small cell lung carcinoma.