It has been postulated that the preliminary steps of cancer known as "cancerization field" could be mediated by a competitive mechanism among mutated and wild-type cells. Cell competition is a process of selection among populations of cells with different fitness: the best adapted cells (winners) survive and proliferate in the tissue at the expense of the less well adapted cells (losers), and these loser cells are eliminated from the tissue by apoptosis. However, the molecular mechanisms mediating this process and the genes involved are still unknown. A mechanism of cell-to-cell communication during cell competition known as the "flower code" has been recently proposed to distinguish loser from winner cells: fwe(ubi) isoform is expressed ubiquitously in the imaginal disc while fwe(Lose) isoforms are expressed specifically during cell competition in the cells to be eliminated. Cell competition has been postulated to have implications in development, tissue homeostasis, regeneration and tumour development; the process of cell competition does not affect the total cell number and organ morphology is maintained because winner cells compensate for the loss. A role of cell competition as the mechanism occurring during initial stages of tumour formation is currently under study.