Spontaneously metastasizing variants derived from MNU-induced rat mammary tumour

N-methyl-N-nitrosourea (MNU) given i.v. to female rats of inbred strains induces mammary adenocarcinomas which are hormone-sensitive but do not spontaneously metastasize (Williams et al., 1981). Tissue culture and selection techniques have been used to derive metastasizing tumours from a mammary tumour induced with MNU in F344/N rats. Histologically, primary tumours and metastases in the lung and lymph nodes were similar. These systems may constitute useful models for the study of breast-cancer metastasis.