We study a mathematical model of cohabitation of healthy and unhealthy stem cells, in order to address some new biological concerns. In short, we will investigate the existence and the stability properties of a positive steady state of a model that is well adapted to the study of dormancy of cancer stem cells. Mathematically, we are concerned with the analysis of a nonlinear retarded system coupled to a nonlinear differential-difference system, in the time-domain framework, via a Lyapunov-like method.