ERBB2 (also HER2) is a transmembrane receptor that is a member of the ERBB family of receptor tyrosine kinases. ERBB2 is altered by amplification and/or overexpression in various cancers, most frequently in breast, esophagogastric and endometrial cancers. Somatic mutations in ERBB2 have been identified in a series of tumors including lobular breast, lung adenocarcinoma, and gastric cancers, among others, with recurrent hotspot alterations in both the extracellular and kinase domains. Preclinical and clinical studies have demonstrated that many of these mutations are transforming and sensitive to FDA-approved ERBB targeted therapies, including trastuzumab, ado-trastuzumab emtansine, lapatinib, and pertuzumab. The ERBB2 p.G776delinsVC variant is one of the in-frame insertions in exon 20 of ERBB2 that have been described in lung adenocarcinoma. Overall, in-frame ERRB2 insertions in exon 20 have been reported in approximately 6% of cases of lung adenocarcinoma which are negative for EGFR, KRAS, ALK alterations and these variants are more frequent in patients who were never-smokers. In vitro studies have shown that this specific variant is associated with constitutive kinase activation and is associated with sensitivity to some ERBB2 inhibitors and therefore, it may represent a targetable mutation in some clinical settings. Please refer to clinicaltrials.gov for additional information. Recommend correlation with other clinical and laboratory findings.