Theories of cancer: how the ideas connect

The mainstream trunk runs left to right along the top of the diagram. The somatic mutation theory (cancer starts when one cell accumulates mutations in growth-controlling genes) was refined into the driver and passenger model (only a handful of those mutations matter) and then set in motion by clonal evolution (Nowell 1976: the mutant cell's descendants compete, diversify and are selected, including by treatment). The hallmarks of cancer (Hanahan and Weinberg 2000, 2011, 2022) sit at the end of the trunk as a synthesis: whatever the origin, cancers converge on the same acquired capabilities.

Below the trunk are the theories that challenge or extend it. The aneuploidy theory (Boveri, Duesberg) says broken chromosomes, not point mutations, are the engine; modern work on chromosomal instability and chromothripsis has absorbed it as an accelerator rather than the sole cause. The epigenetic progenitor theory (Feinberg) says the first step is a reversible change in gene regulation, not a mutation, and it feeds the cancer stem cell and plasticity view (Dick, Weissman, Clevers), in which a tumour is a caricature of a tissue with a stem-like compartment that treatment misses. The metabolic theory (Warburg, Seyfried) puts damaged respiration first; its modern reading (Vander Heiden, Thompson) treats metabolic rewiring as a consequence of oncogenic signalling that is nonetheless druggable. The atavistic theory (Davies, Lineweaver, Vincent) frames all of this as a reversion to an ancient unicellular survival programme.

The tissue-level theories occupy the bottom row. The tissue organisation field theory (Sonnenschein and Soto) says cancer is a disease of tissue architecture in which mutations are secondary; the microenvironment and inflammation view (Virchow, Dvorak, Coussens, Bissell) says stroma, vessels and immune cells co-create the tumour; Paget's seed and soil hypothesis applies the same logic to where metastases grow; the immune surveillance and immunoediting theory (Burnet, Thomas, Schreiber) says the immune system continuously removes nascent tumours and sculpts the ones that survive. The ageing tissue view (DeGregori, Martincorena, Ebert) adds time: mutant clones fill normal tissue throughout life and cancer arrives when old tissue changes what is selected. The newest proposals are physical: the mechanical theory (Bissell, Weaver, Jain) treats stiffness and pressure as instructive signals, and the bioelectric theory (Levin) treats membrane voltage patterns as a tissue-level control layer that can override mutations in animal models.

The arrows record how the schools relate. Solid arrows mean one theory feeds another (driver mutations feed clonal evolution; inflammation and immune escape became hallmarks). Inhibiting arrows mean one theory was proposed against another (tissue organisation, aneuploidy, epigenetics, metabolism and bioelectricity were each framed as alternatives to the somatic mutation theory). In practice the field has stopped treating them as rivals: the 2022 hallmarks paper explicitly imports non-mutational epigenetic reprogramming, phenotypic plasticity, the microbiome and senescence, and the somatic mutation theory is now read as necessary but not sufficient.

Status: a scorecard rather than one verdict. Established: somatic mutation theory, driver and passenger model, clonal evolution, immune surveillance and immunoediting, seed and soil, hallmarks as a framework. Partly confirmed: cancer stem cells (real hierarchy in leukaemias, rigid hierarchy replaced by plasticity), epigenetic progenitor theory, aneuploidy and chromosomal instability, metabolic reprogramming, ageing tissue as a field, mechanical theory. Contested: tissue organisation field theory, atavistic theory, bioelectric theory. Superseded: the strong forms of the aneuploidy theory (chromosomes instead of genes) and of the metabolic theory (respiration damage as the origin), and Ewing's purely mechanical account of metastatic spread.