Is cancer one disease or many diseases? There are many ways to classify cancers: based on where they originate in the body, whether or not they involve solid tumors, and many other features. Plutynski (2018) challenges the presupposition of this question and argues that there is no single correct answer. She illustrates that the variety of classifications comes from different epistemic aims (such as diagnosis, prognosis, treatment, or understanding) and argues for a pragmatic pluralist stance. Building on Plutynski’s account, I discuss the question of whether cancer is one disease or many diseases as follows: Cancer's heterogeneity can be understood in different ways; for example, it may be a single heterogeneous disease with multiple manifestations or many fundamentally different diseases. In medicine, we differentiate diseases because they matter for diagnosis, prognosis, or treatment. I argue that for identifying cases that clinically matter as different cancer diseases (or a single disease), (1) we should clarify what we mean when we use the ambiguous term ‘cancer’, for example, whether it refers to cancer cells or a state of disease, (2) it should be clear what cancer is as a ‘disease’ and what makes cancer a disease, and (3) we should understand how we can utilize the plurality of classifications in identifying and differentiating cases with clinical importance as different diseases. Drawing on insights from the disease entity and dispositional models of disease (Benjamin Smart, 2025), I propose a hybrid model for understanding cancer that clarifies the contributions of different classification targets in identifying cases of disease.
