  We study an evolutionary system of Cahn-Hilliard-Darcy type including mass
source and transport effects. The system may arise in a number of physical
situations related to phase separation phenomena with convection, with the main
and most specific application being related to tumoral processes, where the
variations of the mass may correspond to growth, or shrinking, of the tumor. We
prove existence of weak solutions in the case when the configuration potential
for the order parameter $\varphi$ is designed in such a way to keep $\varphi$
in between the reference interval $(-1,1)$ despite the occurrence of mass
source effects. Moreover, in the two-dimensional case, we obtain existence and
uniqueness of strong (i.e., more regular) solutions.
