Water retention in the tissue can also be designated as a tumour. All tumours are not necessary malignant. In terms of cell propagation, tumours may arise from all living cell structures.
A benign tumour does not grow indefinitely or displace the surrounding tissue.
A malignant tumour is characterised in that it is grows unstoppably. It not only displaces and destroys the surrounding tissues but also forms secondary tumours (metastases).