Different decompositions (sum rules) for the proton mass have been proposed in the literature. All of them are related to the energy-momentum tensor in quantum chromodynamics. In this talk, I report on recent work where we review and revisit these decompositions by paying special attention to recent developments with regard to the renormalization of the energy-momentum tensor. The connection between the sum rules is discussed as well. I present numerical results for the various terms of the mass decompositions up to 3 loops in the strong coupling, and consider their scheme dependence. The role played by the trace anomaly and the sigma terms will be discussed as well. I will also discuss how, according to the current state of research, a future electron-ion collider might be able to contribute to the understanding of the proton mass decomposition.