An ex vivo method for removal of tumor cells from intraoperatively salvaged blood comprising the following steps: - providing intraoperatively salvaged blood which may contain tumor cells outside the human body; - contacting said intraoperatively salvaged blood with at least one trifunctional bispecific antibody, wherein said at least one trifunctional bispecific antibody comprises the following properties: a) binding to a pan-leukocyte antigen, which is selected from at least one member of the group consisting of CD11a, CD15, CD18, CD29, CD39, CD45, CD48, CD52, CD55, CD58, CD59, CD82, CD95, CD97, CD122, CD124, CD132, and CDw137; b) binding to a tumor-associated antigen on a tumor cell; c) binding via its Fc-portion to an Fc-receptor positive cell, said at least one trifunctional bispecific antibody being capable of forming a 3-dimensional network at least with tumor cells and leukocyte cells contained in the blood, wherein said trifunctional bispecific antibody is contacted with said intraoperatively salvaged blood for a time period of 10 - 240 minutes, preferably 10 - 180 minutes, which is sufficient to cross-link tumor cells comprising said tumor-associated antigen and leukocyte cells comprising said pan-leukocyte antigen, and/or other tumor cells in order to obtain associates and/or aggregates comprising said at least one trifunctional bispecific antibody, wherein said tumor cells, said other tumor cells and said leukocyte cells are potentially present in the intraoperatively salvaged blood, and wherein said tumor cells are specifically recognized by said at least one trifunctional bispecific antibody; and - mechanically removing said associates and/or aggregates from said intra-operatively salvaged blood. - providing intraoperatively salvaged blood which may contain tumor cells outside the human body; - contacting said intraoperatively salvaged blood with at least one trifunctional bispecific antibody, wherein said at least one trifunctional bispecific antibody comprises the following properties: a) binding to a pan-leukocyte antigen, which is selected from at least one member of the group consisting of CD11a, CD15, CD18, CD29, CD39, CD45, CD48, CD52, CD55, CD58, CD59, CD82, CD95, CD97, CD122, CD124, CD132, and CDw137; b) binding to a tumor-associated antigen on a tumor cell; c) binding via its Fc-portion to an Fc-receptor positive cell, a) binding to a pan-leukocyte antigen, which is selected from at least one member of the group consisting of CD11a, CD15, CD18, CD29, CD39, CD45, CD48, CD52, CD55, CD58, CD59, CD82, CD95, CD97, CD122, CD124, CD132, and CDw137; b) binding to a tumor-associated antigen on a tumor cell; c) binding via its Fc-portion to an Fc-receptor positive cell, said at least one trifunctional bispecific antibody being capable of forming a 3-dimensional network at least with tumor cells and leukocyte cells contained in the blood, wherein said trifunctional bispecific antibody is contacted with said intraoperatively salvaged blood for a time period of 10 - 240 minutes, preferably 10 - 180 minutes, which is sufficient to cross-link tumor cells comprising said tumor-associated antigen and leukocyte cells comprising said pan-leukocyte antigen, and/or other tumor cells in order to obtain associates and/or aggregates comprising said at least one trifunctional bispecific antibody, wherein said tumor cells, said other tumor cells and said leukocyte cells are potentially present in the intraoperatively salvaged blood, and wherein said tumor cells are specifically recognized by said at least one trifunctional bispecific antibody; and - mechanically removing said associates and/or aggregates from said intra-operatively salvaged blood.