One axiom. One operation. Zero free parameters. Cancer is cells dividing when they should stop, failing to mature, and becoming immortal. This paper forces what that failure is, structurally. In the fold, differentiation is folding to a fixed point — a mature cell has descended to its differentiated lock, the stable state it folds into and stays. Cancer is the lost descent: the orbit that fails to lock, keeps cycling instead of folding down to the fixed point, and so divides without end. Because it never settles into the mortal transient pathway that ends in senescence, it becomes an eternal orbit — the same immortality belonging to the germ line, seized illicitly. Dedifferentiation and unlimited division are one fact: the cell never descended to its fixed point, so it is neither specialised nor stopped. Machine-checked; reproduces from one command. A standalone result within the Smithian Fold Theory of Everything (SFTOE). Full corpus, code, and the run-it-yourself VERIFY.md protocol: https://github.com/MettaMazza/Smithian-Fold-Theory
Maria Smith (Mon,) studied this question.