Normally, the division of cells that occurs continually to maintain number is under very tight control. The genes themselves are made up of DNA, the master genetic blue-print material. If the genes are damaged, say by chemicals or radiation, the control over cell division may be lost in one particular cell.
Stomach cancer starts in a single cell .
That cell starts dividing haphazardly, making millions and billions of copies of itself. It takes up the nourishment needed by other cells, depriving them so the cancer can continue to grow. Quickly growing cells can clump up to form a tumour . The medical name for stomach cancer is gastric cancer. They are subsequently named adenocarcinomas.