RATIONALE: Biological therapies, such as agatolimod, may stimulate the immune system in different ways and stop tumor cells from growing. Monoclonal antibodies, such as trastuzumab, can block tumor growth in different ways. Some block the ability of tumor cells to grow and spread. Others find tumor cells and help kill them or carry tumor-killing substances to them. Giving agatolimod together with trastuzumab may kill more tumor cells.