Figure 2.

Multi-state carcinogenesis: a) the schema shows the progression of different qualitative states (x₁, x₂....x_n-1, x_n) identifiable in the development of cancer from normal tissue. The time parameter (t₀, t₁... ....t_n-1, t_n) depends on a large number of variables interconnected in many ways in a non-linear manner. This makes it extremely difficult to predict the exact time interval between two successive states. Although carcinogenesis is a continuum, its differentiation into successive states is still based on differences in histological and clinical data. Examples of dynamical view of colorectal (b) pancreatic (c) and liver (d) carcinogenesis [38,50,51].