Ewing sarcoma cancer cell, confocal light micrograph. A fluorescent marker has been used to highlight integrins (white). The nucleus is stained orange. Integrins are transmembrane receptors that help the cell to bind to the extracellular matrix and that play a role in cellular mobility. Ewing, or Ewings, sarcoma is a rare malignant (cancerous) tumour of bone tissue. It is most common in teenagers and young adults and is most likely to occur in the pelvis and long bones. Very rarely it can occur in the soft tissues around a bone. Magnification: x630 when printed at 10cm.