Abstract. Motivated by the widespread use of hybrid-discrete cellular automata in modeling cancer, two simple growth models are studied on the two dimensional lattice that incorporate a nutrient, assumed to be oxygen. In the first model the oxygen concentration u(x,t) is computed based on the geometry of the growing blob, while in the second one u(x,t) satisfies a reaction-diffusion equation. A threshold θ value exists such that cells give birth at rate β(u(x,t)-θ)+ and die at rate δ(θ-u(x,t))+. In the first model, a phase transition was found between growth as a solid blob and ``fingering'' at a threshold θc=0.5, while in the second case fingering always occurs, i.e., θc=0.5.