Netti et al (2000) found that the amount of collagen in tumours correlated inversely with the diffusion coefficient of macromolecules, and collagenase treatment of the tumour increased the diffusion coefficient. Pluen et al (2001) provided further support for the role of collagen by measuring diffusion in tumours grown in subcutaneous tissue and the cranium. Hyaluronidase, on the other hand, is reported to reduce the diffusion coefficient of albumin in lung interstitium (Qiu et al, 1999). Here, ALB is linked to neoplasm.