Attempts to develop novel immunotherapeutic mouse models have been hampered by the lack of an adequate in vivo system. This study was performed to establish an immunocompetent mouse model for the testing of immunotherapy concepts. The in vivo system was based on a syngeneic mouse ovarian surface epithelium (MOSE) cancer, physiologically and biologically closely resembling human epithelial ovarian cancer. In addition, a more aggressive variant containing a mutated form of vascular epithelial growth factor was also evaluated. The growth patterns of these ovarian cancer cells in mice were compared to the established, highly aggressive 4T1 breast cancer model. A clinically-relevant tool for the study of different growth patterns in ovarian cancer, with potential significance for the development of novel immunological methods, was successfully developed.