Squamous-cell carcinomatoid tumors occurred in the skin of chickens previously treated with methylcholanthrene. These neoplasms spontaneously regressed until they completely disappeared. This regression was accompanied by degeneration of the epithelial cells, which is most marked at the periphery of the growth. Leukocytes and mononuclear cells infiltrated the periphery of these tumors, apparently to phagocytize the cellular debris. A proliferation of reticulin also occurred at the periphery of these regressing neoplasms. Cortisone acetate resulted in a marked depletion of leukocytes and mononuclear cells about these tumors; however, degeneration of the epithelial cells was essentially the same in cortisone- and noncortisone-treated chickens.

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This investigation was supported by a research grant C-1469 (3C) from the National Cancer Institute of the National Institutes of Health, Public Health Service, and the Tobacco Industry Research Committee. The cortisone was supplied by Merck and Company, Rahway, New Jersey. Doctor Russell Couch, Professor of Nutrition, Texas Agricultural and Mechanical College, supplied some of the chickens. We acknowledge appreciation for the above support.

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