The immune system consists of different kinds of cells and substances which help fight against infections and inflammation in the body. These antibodies and T-cells are part of the immune system that may also help to fight against tumor cells. One way to make antibodies and stimulate T-cells is to inject the patient with a preparation which contains material that may stimulate the immune system. This process is called an immunization. We are trying to immunize the patient against HER2/neu. In order to participate in this trial, the tumor must have a large amount of HER2/neu on its surface. The injection that the patient will receive in this trial is a piece of DNA made in bacteria which contains the gene for rat HER2. DNA is material which contains the information needed to produce many substances in the body. The HER2 gene encodes for a protein known as HER2.