Secreted protein acidic and rich in cysteine (SPARC), also named as osteonectin or BM-40, is an acronym for “secreted protein, acidic and rich in cysteine”. Mature human SPARC shows 92%, 92%, 97%, 99%, 96% and 85% aa identity with mouse, rat, canine, bovine, porcine and chick SPARC. SPARC is the founding member of a family of secreted matricellular proteins with similar domain structure. It is produced by fibroblasts, capillary endothelial cells, platelets and macrophages, especially in areas of tissue morphogenesis and remodeling. SPARC is required for the collagen in bone to become calcified but is also involved in extracellular matrix synthesis and promotion of changes to cell shape. The gene product has been associated with tumor suppression but has also been correlated with metastasis based on changes to cell shape which can promote tumor cell invasion.