The anti-HER2 5F7GGC Nanobody radioiodinated via the residualizing agent N-succinimidyl 4-guanidinomethyl 3-125/131I-iodobenzoate (*I-SGMIB-Nanobody) has superior targeting of HER2-positive human breast carcinoma in vitro and in vivo than its directly radioiodinated counterpart, as *I-SGMIB-Nanobody has enhanced tumour retention of radioactivity [34]. The gene discussed is ERBB2; the disease is neoplasm.