I argue that ductal carcinoma in situ (DCIS), the tumor most commonly diagnosed by breast mammography, cannot be confidently classified as cancer, i.e. as pathological. This is because there may not be dysfunction present in DCIS – as I argue based on its high prevalence and the small amount of risk it conveys – and thus DCIS may not count as a disease by dysfunction-requiring approaches, such as Boorse’s Biostatistical Theory and Wakefield’s Harmful Dysfunction Account. Patients should decide about treatment for DCIS based on the risks it poses and the risks and benefits of treatment, not on its disease status.