A set of contiguous and partially overlapping cDNA sequences and polypeptides encoded thereby, designated as BS249 and transcribed from breast tissue, is described. These sequences are useful for the detecting, diagnosing, staging, monitoring, prognosticating, in vivo imaging, preventing or treating, or determining the predisposition of an individual to diseases and conditions of the breast, such as breast cancer. Also provided are antibodies which specifically bind to BS249-encoded polypeptide or protein, and agonists or inhibitors which prevent action of the tissue-specific BS249 polypeptide, which molecules are useful for the therapeutic treatment of breast diseases, tumors or metastases