Figure 1.

Schematic representation of proposed mechanisms for formation of field defect. A: A mutation or epigenetic alteration in a stem cell (depicted in red) is inherited by all cells within the crypt through niche succession. Crypt fission results in several crypts becoming biologically altered creating a patch defect. Further mutation within this field of altered mucosa leads to malignant transformation; B: Tumour secretes chemical signals that alter the adjacent mucosa resulting in a field defect; C: Malignant cells shed from a tumour travel in the bloodstream and seed in a distant site rendering the mucosa susceptible to malignant transformation.