NOTCH1 is a transmembrane receptor that plays a role in various cellular processes including cell fate determination, growth, and survival. NOTCH1 may be somatically mutated in a variety of cancers, and these mutations can be either gain- or loss-of-function mutations depending on the tumor type. Translocations and activating somatic mutations in NOTCH1 have been identified in T-cell acute lymphoblastic leukemia and chronic lymphocytic leukemia. On the other hand, NOTCH1 loss-of-function somatic mutations are more common in solid tumors, namely squamous cell carcinomas, and occur as missense, frameshift or nonsense mutations. Somatic NOTCH1 mutations are rare in lung adenocarcinoma and are found in about 4% of cases. The NOTCH1 L2457V variant identified in this case has been reported as a benign germline finding in ClinVar (https://www.ncbi.nlm.nih.gov/clinvar/variation/380420/). These results should be interpreted in the clinical context.