Graphical solutions of ordinary differential equations for simplified processes of heat flow in fluids (Lorenz system) and an idea of common mathematical description are the basis for the proposed thermodynamical leukemia model. The model provides description of remission and relapse in leukemia as two hierarchical states of normal hematopoiesis. Transition between them is possible through a pitchfork bifurcation. Relapse and remission are considered as common symmetrical manifestations of the phase space changes in leukemia, which also explains phenomenon of spontaneous remission. Cytopenia is regarded as an adaptive reaction of hematopoiesis to entropy increase caused by leukemia clone. The following hypotheses are formulated: a) Percentage of leukemia cell in marrow for relapse or remission criterion is not a strict cut-off constant but a variable value; b) Probability of getting remission depends upon reaching bifurcation; c) Duration of remission depends upon eradication of leukemia cells in induction and consolidation.