The present report describes the various types of tumors which developed in female Sprague-Dawley rats oophoreetomized at age 46 days and fed a single dose of 20 mg 7,12-dimethylbenz(a)anthracene one week later. This method, which is known to induce breast carcinoma invariably in normal female rats of this strain, produced mammary cancer in only 5% of the oophorectomized rats, after a period of observation of about a year. In contrast, a high percentage of rats presented tumors of the ear duct

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... 59%), neurofibrosareomas of the ear lobe (64%), and various tumors of the skin and skin appendages (22%). The appearance of these extramammary tumors may be due in part to the longer lifespan of the rats because they escaped the lethal effects of breast carcinoma. However, a relationship between carcinogenic reactivity of the skin and the endocrine status of the host cannot be ruled out.