ERBB2 encodes a transmembrane receptor tyrosine kinase that plays crucial roles in cell proliferation, migration, and survival through multiple signaling pathways. The protein functions primarily through heterodimerization with other ERBB family members, particularly ERBB3, to activate downstream PI3K-AKT signaling cascades 1. Beyond its canonical plasma membrane localization, ERBB2 also functions in the nucleus where it regulates transcriptional programs, including activation of PTGS2/COX-2 and CDKN1A gene expression. ERBB2 is overexpressed in 15-20% of breast cancers and is associated with enhanced glycolytic metabolism through upregulation of hexokinases HK1 and HK2, promoting tumor cell proliferation, migration, and invasion 2. The protein also cooperates with other oncogenic factors like ECD to enhance unfolded protein response and glycolytic pathways in tumorigenesis 3. Loss-of-function variants in ERBB2 can cause developmental disorders, as homozygous or heterozygous variants result in Hirschsprung disease and chr17 intestinal pseudo-obstruction through impaired enteric nervous system development 4. Clinically, ERBB2 represents a major therapeutic target with multiple approved drugs including trastuzumab (Herceptin), afatinib, dacomitinib, and antibody-drug conjugates like disitamab vedotin, though resistance mechanisms involving splice variants like p95-ErbB2 continue to pose therapeutic challenges 51.