EGFR and neoplasm: In bone metastases, the percentage of EGFR-positive tumour cells frequently reached 100% per tumour sample (Fig. 4e) and its mean value was significantly higher than in the cohort of EGFR-positive primary tumours (92%, n = 13 vs. 58%, n = 1258; two-tailed Mann–Whitney test, p < 0.0001).