Induction of malignant lymphomas in swiss mice by N‐nitroso compounds formed in vivo

Malignant lymphomas were induced in Swiss mice treated intragastrically with methyl-2-benzimidazole carbamate (MBC, BCM, Carbendazim) and given sodium nitrite in their drinking water. The tumours appeared between 82 and 164 days after the beginning of treatment. In 30 mice given MBC and sodium nitrite, 10 lymphosarcomas were found. In the proliferating tumour cells, intracytoplasmic type-A virus particles were demonstrated by electron microscopy. No tumours were found in animals given MBC only. The findings demonstrate the possibility of in vivo formation of N-nitroso derivatives from MBC.