NOTCH1 is a transmembrane receptor, which plays a role in cell fate determination, growth, and survival. Notch signaling has been demonstrated to play a role in lung development and lung carcinogenesis. Notch activity is counteracted by NUMB. Gain-of-function mutations of NOTCH1 have been identified in approximately 10% of patients with non-small cell lung carcinoma (NSCLC). In addition, loss-of-function mutations in NUMB that allow for increased NOTCH1 activity have been observed in approximately 30% of NSCLC patients. Studies have observed that increased NOTCH1 expression is associated with a poor prognosis in patients with lung adenocarcinoma. The NOTCH1 intronic deletion variant (NM_017617:g.139397792_139397795del) is located nine base pairs downstream of exon 27. While the variant is located in close proximity to an exon-intron junction, a potential effect on gene splicing is unknown. These results should be interpreted in the clinical context.