Pathology of tumors developed in guinea pigs given intraperitoneal injections of N-methyl-N-nitrosourea.

The carcinogenic effects of N-methyl-N-nitrosourea after repeated intraperitoneal administration in inbred strain NIH 13 guinea pigs were studied. 50% of the animals that survived beyond 22 weeks, after intraperitoneal injection of MNU at a dose of 10 mg/kg body weight/week for 18 weeks, developed a broad spectrum of tumors: these included adenocarcinoma of pancreas in 2 animals, fibrosarcoma of the mesentery in 2 animals, angiosarcoma of mesentery in 2 animals, mesothelioma of the peritoneum in 1 animal and tumors of small intestine in 3 animals. These studies indicate the susceptibility of different types of tissue to the local effects of MNU after intraperitoneal administration.