Patient Clinical Scenario: Second-Line Treatment of Metastatic NSCLC With HER2 MutationsThe clinical scenario involves a 73-year-old Asian female diagnosed with stage 4 non–small cell lung adenocarcinoma harboring a HER2 exon 20 insertion mutation, specifically, the most commonly observed A775_G776 insertion (YVMA). This patient represents a typical presentation for HER2-–mutated lung cancer, occurring in an older Asian female patient population. The molecular profile confirms the presence of the classic HER2 exon 20 insertion mutation that drives oncogenic signaling and represents the primary therapeutic target for HER2-directed interventions. Following the induction phase, the patient transitioned to maintenance therapy with pemetrexed and pembrolizumab, representing standard practice for maintaining disease control after initial chemotherapy response. The treatment course demonstrates the typical progression of care for HER2-mutated patients prior to the availability of targeted therapeutic options.