ERBB2 and neoplasm: The advantages of [64Cu]trastuzumab, [68Ga]trastuzumab F(ab′)2 fragments, [68Ga]ABY-002, and [89Zr]trastuzumab PET/CT over biopsy-guided detection of HER2 expression include the ability to assess HER2 expression of the entire tumor volume (which addressing the intrinsic heterogeneity of HER2 expression), directly assessing the binding of the therapeutic mAb (trastuzumab) to HER2, and assessing the response to therapy.