RecruitingPhase 2Biological interventionTrial of Therapies With IT cDC1s Combined w/ IT Trastuzamab for Her+ or IT Nivolumab for Her- BC LMDThe purpose of this study is to learn about the effects of the study treatment, Dendritic Cell Vaccine (DCV), in combination with trastuzumab or nivolumab to confirm the highest dose of the study treatment that can be given safely to participants with Breast Cancer (BC) with Leptomeningeal Disease (LMD).