Tumours are not always dangerous. Indeed there are some tumours such as warts which are very common and harmless. These are called benign tumours and the reason that they are harmless is because they do not spread.
Benign tumours stay in one place and usually stop growing when they are quite small.
The dangerous type of tumours, the ones that we call cancers, are the ones which can spread into the surrounding body tissues and, eventually, around the body. At the Hadassah-Hebrew University Hospital in Jerusalem, AICR is supporting the research of Dr Israel Vlodavsky, who is investigating the way that cancers spread and, in particular, the involvement of a protein called heparanase in the spread of cancer cells. An important step towards understandingwhy cancer cells spread Currently, we do not fully understand how malignant cancer cells are able to spread into neighbouring tissues in the body. However, it seems very likely that, before they can spread, the cancer cells have to break down the material holding normal cells together, so they can squeeze between them. Normal cells produce an extracellular matrix, which is a complex mixture of proteins and sugar molecules that binds cells together.