SBEM is a 90 amino acid secreted membrane protein that may play a role as marker for the diagnosis of metastatic breast cancer. SBEM contains three tandem copies of a neutral octapeptide core repeat, and its N- and C-terminal regions are charged and fairly polar. These features are similar to many sialomucins, although the SBEM protein lacks a transmembrane domain and is shorter than most other known epithelial mucins. Expressed in mammary, salivary glands, prostate and also in lung, SBEM is mainly expressed in cancer cell lines of breast origin. SBEM is also highly expressed in lymph node-positive compared with node-negative tumors and in all lymph node containing metastatic cells. The SBEM gene is conserved in chimpanzee, cow, mouse, rat, chicken, zebrafish, C.elegans and M.grisea, and maps to human chromosome 12q13.2.