CD44 and cancer: It has been shown ex vivo41 and in vivo18 that it can give rise to MT signal, and it is abundant in the stroma of preclinical cancer models and in patients.42 Ovarian cancer ECM consists of collagen IV, fibrillar collagens, hyaluronan and heparan sulfate proteoglycans (extensively reviewed42), and although the fibrillar collagen type I distribution visualised with SHG contrast was spatially correlated to MT signal, it is possible that other ECM proteins also contributed to the macromolecule signal in imaged tumour models as well.