Complex multicellular organisms require quantitative and qualitative assessments 
on each of their constitutive cell types to ensure coordinated and cooperative 
behavior towards overall functional proficiency. Cell competition represents one 
of the operating arms of such quality control mechanisms and relies on fitness 
comparison among individual cells. However, what is exactly included in the 
fitness equation for each cell type is still uncertain. Evidence will be 
discussed to suggest that the ability of the cell to integrate and collaborate 
within the organismal community represents an integral part of the best fitness 
phenotype. Thus, under normal conditions, cell competition will select against 
the emergence of altered cells with disruptive behavior towards tissue integrity 
and/or tissue pattern formation. On the other hand, the winner phenotype 
prevailing as a result of cell competition does not entail, by itself, any 
degree of growth autonomy. While cell competition per se should not be 
considered as a biological driving force towards the emergence of the neoplastic 
phenotype, it is possible that the molecular machinery involved in the 
winner/loser interaction could be hijacked by evolving cancer cell populations.