  We derive a continuum mechanical model to capture the morphological changes
occurring at the pretumoral stage of epithelial tissues. The proposed model
aims to investigate the competition between the bulk elasticity of the
epithelium and the surface tensions of the apical and basal sides. According to
this model, when the apico-basal tension imbalance reaches a critical value, a
subcritical bifurcation is triggered and the epithelium attains its
physiological folded shape. Based on data available in the literature, our
model predicts that pretumoral cells are softer than healthy cells.
