Cancer is a clinical term applied to malignant epithelial new growths. From the pathologist's
point of view it may be defined as an epithelial tumor which infiltrates, and which may give
rise to metastases. To understand the full significance of this definition it is necessary to
study in groups by themselves all the tumors which arise from each variety of normal
epithelial cells and which tend to differentiate like them. Each group has peculiarities of its
own. The tendency is steadily increasing to place together and study in a group by …