Non-angiogenic tumours unveil a new chapter in cancer biology.

The term 'angiogenesis' was coined in 1787 and the role of vessels in cancer has been studied ever since. In 1971 Folkman introduced the hypothesis, until now widely accepted, that tumour growth is strictly dependent on angiogenesis. However, the discovery that tumours can also grow without angiogenesis by exploiting pre-existing vessels, both in humans and more recently in mice, has demonstrated that this is not always the case. These observations highlight a new aspect of the interaction between vessels and tumours and demonstrate the existence of a previously unrecognized group of tumours that grow without angiogenesis and whose biology is, so far, largely unknown.