Recent Progress in the Microscopic Anatomy and Differentiation of Cancer

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 themselves all the tumors built up from the multiplication of single type-cells which tend to differentiate in a similar manner. As example of type-cells may be mentioned the fibroblast, the smooth muscle cell, the neuroglia cell. It must be borne in mind, however, that two or more varieties of the same type-cell often exist normally. For example we have