Invasive mucinous adenocarcinoma harbored MET exon 14 skipping mutation: case report.

Background: Lung mucinous adenocarcinoma has various genetic alterations, but there are no reported cases with MET exon 14 skipping mutations. Multiplex genetic testing is commonly assessed in non-small cell lung cancer (NSCLC) and treatment usually comprises molecular targeted drugs. However, the efficacy of molecular targeted drugs in lung mucinous adenocarcinoma is not reported. Here, we report on the clinical features of tepotinib in invasive mucinous adenocarcinoma (IMA) harboring MET exon 14 skipping mutation.

Case description: A 68-year-old Japanese woman was diagnosed with IMA that harbored MET exon 14 skipping mutation. Initial treatment targeting community-acquired pneumonia or cryptogenic organizing pneumonia was ineffective. Blood carcinoembryonic antigen had increased, and positron emission tomography showed uptake of ¹⁸F-fluorodeoxyglucose on the infiltration. A second trans-bronchial lung biopsy allowed diagnosis of IMA that harbored MET exon 14 skipping mutation. Tepotinib 500 mg once daily was initiated as the patient's first-line treatment and she showed a durable response with mild adverse events during treatment.

Conclusions: Molecular targeted drugs (tepotinib) showed similar efficacy for IMA harboring MET exon 14 skipping mutation to their use for NSCLC. This case suggests the benefit of aggressive multiplex genetic testing in patients with IMA and subsequent treatment with molecular targeted drugs.