Extrapolating from ongoing clinical trials with a 68Ga-labeled anti-HER2 sdAb breast cancer PET-tracer [33] and an anti-MMR sdAb macrophage PET-tracer [48], we are hopeful that the future clinical anti-LAG-3 sdAb PET-tracer will be safe, sensitive and conveniently provide a whole-body picture of huLAG-3 expression levels in a same-day imaging procedure with acceptable dosimetry levels. The gene discussed is LAG3; the disease is breast carcinoma.