Further notes on a rat tumor

Abstract

On several occasions we reported to this Society upon a rat tumor that has been transplanted for more than two years. The tumor was originally described as a sarcoma. In a recent report 1 we described its transformation into a malignant adenoma. This change in histological structure was attended with the acquisition of the property, hitherto absent, of producing metastasis in lymphatic glands. The reverse changes, namely from the adenoma into sarcoma, had been noted by Ehrlich, Leo Loeb and others in mouse cancers and were attributed to gradual or rapid proliferation and predominance of the stroma of the tumors or of a corresponding tissue derived from the host. Since our rat tumor underwent the change into adenoma when implanted beneath the skin, the epithelial cells must have arisen from elements present in the graft. The original tumor had been kept and sections were made from different parts of it in an endeavor to discover undoubted evidences of epithelial proliferation. Such evidences were found in several places, but notably in one place, in the glandular tubules or epithelium-lined spaces of the seminal vesicle in which organ the tumor developed originally. Hence there is no longer any doubt of the existence of a carcinomatous element in the original growth although it was restrained by the other and less highly organized parts of the tumor. The carcinomatous elements gradually gained supremacy in one strain of the tumor, then in other strains, until now all the strains which have been kept alive have either gone over into adenoma or are well advanced in this transformation.