The search for new, reliable factors of prognosis in cancerology is sadly deficient at the present moment. Of these factors, the measurement of ploidy gives rise to considerable hope. Nevertheless, despite the impressive number of papers currently published, no general law seems to be emerging that associates the ploidy rate of a tumour with its clinical evolution in a patient. The purpose of the present work is firstly to use a logical automation to describe the cell cycle in terms of binary variables (the validation of the methodology), and secondly to demonstrate that a certain 'cancer logic' can be distilled, at least with respect to the genesis of DNA histograms among tumours.