A careful examination of the literature, not only of the past, but also the present, has convinced me that many of the tumors reported as carcinomata and sarcomata as well as tumors such as Krompecher's "carcinoma endotheliale" or Hansemann's "adenoma endotheliale," are in reality pure endothelial tumors. The latter author even speaks of a "carcinoma sarcomatodes endotheliale," thus combining three distinct groups of tumors in one. Krompecher1 speaks of a "carcinoma endotheliale sarcomatodes," and calls an endothelioma a carcinoma with undifferentiated epithelium, naming it a "carcinoma endotheliale." It can only be an endothelioma which is capable of producing polymorphous structures leading to such complications of names.
The variability in the arrangement of endothelial cells and the ability of these cells to undergo metamorphosis, simulating the epithelial type at one place and the connective tissue type at another, has given rise to great confusion in the diagnosis of tumors. Morphologically,