Lumican (LUM) is also known as Keratan sulfate proteoglycan lumican, KSPG lumican,LDC and SLRR2D, which belongs to the small leucine-rich proteoglycan (SLRP) family and SLRP class II subfamily. LUM /Lumican is present in the extracellular matrix of human articular cartilage at all ages, although its abundance is far greater in the adult. In the adult cartilage LUM /Lumican exists predominantly in a glycoprotein form lacking keratan sulfate, whereas the juvenile form of the molecule is a proteoglycan. LUM participates in the maintenance of tissue homeostasis and modulates cellular functions including cell proliferation, migration, and differentiation. The expression of LUM has been correlated to the growth and metastasis of various malignancies.