Title: Rigorous derivation of a Hele-Shaw type model and its non-symmetric traveling wave solution

Abstract: In this paper, we consider a Hele-Shaw model that describes tumor growth subject to nutrient supply. This model was recently studied in \cite{feng2022tumor} via asymptotic analysis. Our contributions are twofold: Firstly, we provide a rigorous derivation of this Hele-Shaw model by taking the incompressible limit of the porous medium reaction-diffusion equation, which solidifies the mathematical foundations of the model. Secondly, from a bifurcation theory perspective, we prove the existence of non-symmetric traveling wave solutions to the model, which reflect the intrinsic boundary instability in tumor growth dynamics.