Preclinical models that display spontaneous metastasis are necessary to improve therapeutic options for hormone receptor positive breast cancers. In this study, we conducted a detailed cellular and molecular characterization of MCa-P1362, a novel syngeneic Balb/c mouse model of metastatic breast cancer. MCa-P1362 cancer cells expressed estrogen receptors (ER), progesterone receptors (PR), and HER-2 receptors. MCa-P1362 cells proliferate in vitro and in vivo in response to estrogen, yet do not depend on steroid hormones for tumor progression. Further characterization of MCa-P1362 tumor explants shows that they contain a mixture of epithelial cancer cells and stromal cells. Based on transcriptomic and functional analyses of cancer and stromal cells, stem cells are present in both populations. Functional studies demonstrate that crosstalk between cancer and stromal cells promotes tumor growth, metastasis, and drug resistance. MCa-P1362 may serve as a useful preclinical model to investigate the cellular and molecular basis of hormone receptor positive tumor progression and therapeutic resistance.