Surprisingly, overall uptake of [89Zr]Zr-trastuzumab in the MDA-MB-231 (Fig. 3A–B) and MDA-MB-231/H2N (Fig. 4A–B) tumours was not significantly different (18.8 ± 1.4 and 15.1 ± 2.6%ID/g, respectively; P > 0.05), despite the cell lines having different HER2 expression levels (in vitro Bmax values were 18,662 ± 1335 and 47,473 ± 1926 cpm, respectively). This evidence concerns the gene ERBB2 and neoplasm.