NOTCH1 is a transmembrane receptor, which plays a role in cell fate determination, growth, and survival. Somatic activating mutations are common in T-cell lymphoblastic leukemia/lymphoma. Somatic alterations in NOTCH1 are very rare in breast invasive ductal carcinoma and are identified in less than 1% of cases. NOTCH1 L2457V does not lie within any known functional domains of the NOTCH1 protein. L2457V has been identified in sequencing studies, but has not been biochemically characterized and therefore, its effect on protein function is unknown. The L2457V variant has been reported as a benign/likely benign germline variant in ClinVar (https://www.ncbi.nlm.nih.gov/clinvar/variation/380420/). These results should be interpreted in the clinicopathologic context.