Advances in tumor profiling have revealed molecularly distinct cancer subtypes requiring tailored therapies, such as trastuzumab for HER2-positive (human epidermal growth factor receptor 2 positive) breast cancer, cetuximab for KRAS wild-type colorectal cancer, tyrosine kinase inhibitors for chronic myeloid leukemia (CML), gastrointestinal stromal tumors, and non-small-cell lung cancer (NSCLC), and agents like vemurafenib or olaparib in melanoma, ovarian, breast, and prostate cancers. The gene discussed is ERBB2; the disease is cancer.