Here, we describe the case of a patient diagnosed with locally advanced breast cancer 8 years ago. Her treatment course was neoadjuvant chemotherapy, followed by mastectomy and then adjuvant radiotherapy and trastuzumab (TTZ). During the use of adjuvant targeted therapy, an incidental pregnancy was diagnosed. Four years later, she developed bone and cerebral metastases, and since then, she has received courses of TTZ, capecitabine, lapatinib, and radiotherapy with intermittent control of the disease. Her 7-year-old son presents a normal physical and long-term neurological developmental curve according to specialized evaluation. This case is unique for several reasons: the patient received the highest dose of TTZ yet described during pregnancy (4400 mg); there has been a long period of disease-free survival after treatment for locally advanced breast cancer and long overall survival despite successive disease progressions during the metastatic phase of the disease (97 months), and there was a monitored pediatric follow-up period (7 years).