Induction and Differentiation of an Epithelial Tumour in the Newt (Triturus cristatus)

ABSTRACT Epithelial tumours have been induced in T. cristatus by any of several carcinogens. The tumours arise from the mucous glands of the skin. The tumours showed infiltrative and destructive growth, sometimes penetrating into the peritoneal cavity. Metastasis also occurred. The tumours thus appeared to be malignant. In spite of its malignant characteristics this carcinogen-induced epithelial tumour often regressed. This regression of an apparently malignant tumour occurred spontaneously. During regression of the tumour, differentiation of the tumour cells into normal, non-malignant tissues occurred. Expansively growing tumours differentiated independently of their location into pigment cell layers, cornified layers, mucous glands, and epithelium of the integument. In contrast, infiltrating tumours differentiated in accordance with their surroundings and even connective-tissue-like cells were formed. Tumour metastases differentiated by the formation of degenerative mucous cells or in the same ways as expansively growing tumours. If no differentiation occurred, the tumours were lethal. The capacity of newts to bring their tumour cells under control again by a differentiation process is attributed to the great regeneration power of these animals.