Neoplasms of the skin and other organs observed in Swiss mice treated with nitrosoalkylureas.

A number of nitrosoalkylureas, nitrosoalkylcarbamates, and chlorinated nitrosotrialkylureas were painted twice a week on the skin of female Swiss mice at a concentration of 40 mM. Of the 29 compounds, 16 induced skin tumors in 4 or more of 20 mice; 9 compounds produced tumors in 10 or more mice. Most of the skin tumors were squamous cell or basal cell carcinomas, and some sarcomas. These carcinomas and sarcomas of the skin were large, invasive, and in several animals there were multiple large metastases to the lungs and lymph nodes. Treatment with several of the compounds was associated with poor survival. The median survival in many other groups was reduced considerably below the 2-year survival of acetone-treated controls. Many of the treatments led to development of tumors of internal organs, including mammary carcinomas, adenocarcinomas and squamous cell carcinomas of the lung, and tumors of the stomach. The stomach tumors might have arisen through exposure to the compound licked from the skin. It appears that several of the compounds were absorbed through the skin of the mice and exerted their effect systemically.