PI3K-mTOR signalling pathway analyses showed that tumours from patients who did not obtain prolonged remissions (control group) usually had loss of expression in PTEN, PRKAA1 and MAP3K4, as well as overexpression in AGPAT1 and FKBP8. On the contrary, tumours from the Long-HER group could present with none, one or two of these molecular alterations, which suggests that more than two events (either these or other with similar consequences) are needed to confer resistance to trastuzumab. The gene discussed is PTEN; the disease is neoplasm.