Objectives: In cancer treatment, conventional medicine faces an ideological debate about what constitutes the true nature of the disease. Should it focus on the objective view offered by medical technology, the suffering of the patient or the cultural dimensions of a disease shaped by its representations as an evil entity? Main points: With therapeutic effectiveness as a goal, medicine favours a biochemical perspective, dispensing with the cultural dimensions that can nonetheless play a role in treatment acceptance. We would like to demonstrate that the imagery of this disease created by the individual and society allows cancer patients to advance from dependence to subjectivation of the disease that is so profoundly transforming their lives. More broadly, cancer treatment is fostering the development of a new symbolism of evil in a secularised society. Future prospects: We brought to light the active role played by the imagery of cancer and the symbolism of evil. Although we must view the effects of phantasms with care, they can clearly lead to the development of a wider, richer and assimilated interpretation of the suffering self. The symbolism of evil is not a parasite against which medicine must struggle, but rather a revealer of the heuristics of the imagery of evil at the core of medical explication.