RecruitingBiological interventionMulti-CAR T Cell Therapy Targeting CD7-positive MalignanciesThe purpose of this clinical trial is to assess the feasibility, safety and efficacy of CAR T cell therapy against CD7-positive hematological malignancies using CD7 specific CAR T cells. The study also aims to learn more about the function of CD7 CAR T cells and their persistence in patients of hematological malignancies.