Cancer is a group of more than 100 different diseases. It develops when cells in the body undergo genetic changes that interfere with their normal development.
The changed cells may form a mass called a tumour. This tumour can be either benign or cancerous. A benign tumour can grow, but will not spread throughout the body. A cancerous tumour can grow and spread.
Not all cancers form tumours. Types that don’t include leukaemia, most lymphomas, and myeloma.