Histopathology slides from medical research to medical practice in interwar Strasbourg

Histopathologists have been interested in cancer since the beginning of cellular theory. Rudolf Virchow and Julius Cohnheim defined cancer as a disease due to specific changes in tissues; cancer was thus considered a "pathologist's disease." Virchow emphasized the principles of biopsy and its value in the diagnosis of malignant tumours, but he himself did not promote it as an instrument for diagnosis. In the nineteenth century, in fact, cancer was a pathologists' disease in research only, not in diagnosis. By the mid-twentieth century, pathologists figured in medical practice as mediators between alternative therapeutic solutions. Histopathology entered a new arena, medical practice. In this paper, the process through which microscope slides moved from histopathology research to medical practice will be explored in detail with the aim of understanding how medical research integrates routine medical practices. The quasi-inherent character of scientific knowledge as relevant to medical practice is not taken for granted here. Through a study of medical school laboratory records from the interwar period in Strasbourg, I argue that pathologists could direct patients to specific forms of therapy on the basis of microscopic slides of cancer cells because they had defined (and re-defined) cancers by contributing to establishing radiation therapy practices.