ESR1 and invasive ductal breast carcinoma: Also, newer monitoring tools are necessary during a neoadjuvant therapy to help personalize treatment.  Here, we describe the case of a 64-year-old man with Stage IIB (tumor size 2 to 5 cm with involvement of axillary lymph nodes), high-grade estrogen receptor, progesterone receptor, and HER2-positive invasive ductal carcinoma with a germline breast cancer susceptibility gene 1 (BRCA1) mutation who was treated in a neoadjuvant fashion with dual HER2 blockade and platinum-based chemotherapy regimen.