Invasion, metastasis, and tumour dormancy

Abstract

Tumours can be either benign or malignant. A first difference is that the primary malignant tumour infiltrates the surrounding tissue while, with very few exceptions, the benign tumours do not infiltrate. The second and main one is that, by definition, the malignant tumours are able to produce metastatic lesions in other organs. Finally, metastases can declare themselves even after period of years from the appearance of the first lesion. This is because of the third property of the malignant cells i.e. their ability to spread and then do not immediately grow into a detectable metastasis, but to be ‘dormant’ for a variable period.