HER2-CAR T Cells in Treating Patients With Recurrent Brain or Leptomeningeal Metastases

Inclusion Criteria: * SCREENING: Participant has treated brain and/or leptomeningeal metastases that has not recurred OR * Such participants are eligible to enroll in the study and undergo leukapheresis, but they cannot start treatment with HER2-CAR T cells until there is evidence of tumor progression/recurrence * SCREENING: Participant has recurrent brain metastases after radiation therapy OR * SCREENING: Participant has recurrent leptomeningeal metastases after intrathecal chemotherapy OR * SCREENING: Participant has untreated brain or leptomeningeal metastases and refuses to undergo radiation and/or intrathecal chemotherapy * Note: Participants with leptomeningeal metastasis (diagnosed by positive CSF cytology or characteristic findings on brain or spine magnetic resonance imaging \[MRI\]) may have concomitant brain metastases, but having both is not required * SCREENING: Participant must have a Karnofsky performance status (KPS) \>= 70 * SCREENING: Participant must have a life expectancy of \>= 8 weeks * SCREENING: The effects of HER2-CAR T cells on a developing fetus are unknown. For this reason, women of child-bearing potential must have negative serum pregnancy test and agree to use a reliable form of birth control prior to study entry and for at least two months following duration of study participation. Male research participants must agree to use a reliable form of birth control and not donate sperm during the study and for at least six months afterwards * SC…