Ιn two patients with early (Table 2; patient number 6 and number 13) and in four (Table 2; patient number 7, number 11, number 20 and number 22) with metastatic disease, two distinct subpopulations of CTCs, according to the expression status of HER2, could be identified: CTCs expressing the full-length HER2 receptor as well as CTCs expressing the p95HER2 receptor. This evidence concerns the gene ERBB2 and metastatic neoplasm.