Staining mouse tumor sections with anti‐MUC1 nanobody and irrelevant recombinant Llama anti‐GFP nanobody demonstrated a high reactivity for anti‐MUC1 nanobody toward mouse MUC1 but a very low or negligible one for irrelevant recombinant Llama anti‐GFP nanobody (Fig. 4a–d). The gene discussed is MUC1; the disease is neoplasm.