Tumor Heterogeneity

Tumor heterogeneity is the diversity of cell populations within a single tumor, encompassing genetic, epigenetic, and phenotypic variation. This diversity is not random noise but the raw material of tumor evolution: subclones compete for space and resources, cooperate to manipulate the microenvironment, and evolve resistance to therapy. Phylogenetic reconstruction of tumor samples reveals branching evolutionary histories that mirror species-level evolution, complete with clonal expansions and selective sweeps. Understanding tumor heterogeneity is central to designing therapies that anticipate evolutionary escape rather than merely maximizing immediate cell kill. It connects cancer to phylogenetics as an application domain where evolutionary thinking is literally lifesaving, and raises the prospect of managing therapeutic resistance through evolutionary-informed treatment strategies.