first of all thanks for the citation on your last paper in PLOS about Bio modeling by PN.
According to the type of cancer that you want to model, the model representation may differ, requiring different assumptions. The attached file is a summary about two most common types of cancer, tumor staging and structures that are involved in tumor progression (source ACS).
A more detailed explanation of the tumors heterogeneity is reported in attached (slightly complex) clinical paper.
I love Bio-modeling, and if You'll need some advice I'm available. I'm working on not publishable projects, and I would still like to publish something new.