Marleen Kok, MD, PhD, Netherlands Cancer Institute, Amsterdam, Netherlands, shares an update on the MIMOSA trial (NCT04307329) of monalizumab and trastuzumab in metastatic HER2+ breast cancer, and discusses a study of the spatial distribution of lymphocytes versus fibroblasts and it’s use as a prognostic factor. This interview took place at the virtual European Society for Medical Oncology (ESMO) Breast Cancer Congress 2021.