A beautiful and sickening, utterly convincing and heartbreaking passage from Siddhartha Mukherjee's magnificent biography of cancer, The Emperor of All Maladies:
"Gene cascades [involved in the genesis of cancer are] perversions of signaling pathways used by the body under normal circumstances … [in sum] Nothing is invented; nothing is extraneous. Cancer's life is a recapitulation of the body's life, its existence a pathological mirror of our own. Susan Sontag warned against overburdening an illness with metaphors. But this is not a metaphor. Down to their innate molecular core, cancer cells are hyperactive, survival-endowed, scrappy, fecund, inventive copies of ourselves."