title: High incidence of rat mammary carcinoma by oral administration of ethyl methanesulphonate.
abstract: Ethyl methanesulphonate (EMS), one of the alkylating agents, is known to be a potent mutagen. We tested EMS for its carcinogenicity in female rats by oral administration. EMS was dissolved in drinking tap water at a concentration of 10(-3) M and was given for the first 12 weeks. The subcutaneous tumors were noticed as early as 16 weeks after initiating the experiment. At the 32nd week, all the surviving rats produced tumors; the majority were multiple tumors in the neck, axillar and inguinal areas corresponding to bilateral mammary glands. Histologically, the prevailing feature of the tumors was infiltrating medullary adenocarcinoma consistent with carcinoma of mammary duct origin. Neither regional lymph node involvement nor distant metastases were shown, but intraductal spread of carcinoma was a marked finding during the 32-week period.
mesh_terms: D000230:Adenocarcinoma / Q000139:chemically induced* / Q000473:pathology; D000818:Animals; D005020:Ethyl Methanesulfonate / Q000008:administration & dosage*; D005260:Female; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced* / Q000473:pathology; D009361:Neoplasm Invasiveness; D051381:Rats; D013997:Time Factors
chemical_list: D005020:Ethyl Methanesulfonate