For example, SPECT VHHs targeting HER2, which is expressed in approximately 20% of breast cancers, showed high tumor uptake, rapid blood clearance, low accumulation in non-target organs, and high tumor-to-blood and tumor-to-muscle ratios one hour after intravenous injection in HER2-positive mouse breast tumor models [82]. Here, ERBB2 is linked to breast carcinoma.