Crossing paths: historical and philosophical perspectives on cancer and diabetes classifications

No one is perfect, and this is particularly true of disease classifications. When diseases are classified according to different dimensions (topography, symptoms, morphology, aetiology, etc), some characteristics of the diseases are prioritised while others are downplayed. Moreover not all diseases are equally well characterised by a given dimension, and especially complex, chronic diseases such as cancer and diabetes have proved difficult to classify because of their heterogeneity. Their classification created tensions historically and still present challenges today. In this article we juxtapose the difficulties of classifying diabetes and cancer historically with the challenges arising in modern classifications of the two diseases. We trace the history of classifying cancer and diabetes, and find that while cancer proved difficult to classify based on its physiological features, diabetes could not readily be situated anatomically and they were classified according to different dimensions: cancer as patho-anatomical and diabetes as patho-physiological. We then discuss the limitations that come with the adoption of these classifications and how they are currently being challenged by new scientific developments. We show that the use of molecular markers to reclassify diabetes 2 and cancer allows their characterisation to cross paths i.e. to move across the classificatory dimensions that had been prioritised historically. Reopening down-prioritised dimensions comes at a price, though, and, we outline challenges as well as opportunities faced by type 2 diabetes and cancer classification. Finally, we argue that the combination of philosophical and historical analyses is well suited to cast light on classificatory tensions and challenges.