Theseencompassed challenges in tumor material acquisition, such as the observedprevalence of negative HER2 expression in positive PET scans when samplesoriginated from the liver or bone, intratumoral heterogeneity, and drug bindingimpediments to HER2 receptors, which garnered specific attention due to theassociation between a positive biopsy result with diminished[68Ga]Ga-ABY-025 accumulation and a poorer prognosis within themetastatic breast cancer cohort. The gene discussed is ERBB2; the disease is neoplasm.