For this purpose, patients who had secondary metastatic disease were divided into (i) patients with gained HER2 expression (initial HER2 zero and in metastatic tissue HER2 1 + or 2 + /FISH-negative; or initial HER2 1 + and in metastatic tissue HER2 2 + /FISH-negative), (ii) patients with constant HER2 receptor expression and (iii) patients with loss of HER2 expression. The gene discussed is ERBB2; the disease is metastatic neoplasm.