The nude mouse as an in vivo model for human breast cancer invasion and metastasis.

Human breast cancer xenografts only rarely invade and metastasize in nude mice, and have therefore only had limited use as a model for studying mechanisms involved in breast cancer spreading. However, recent reports describe differences not only between various cell lines but also between strains of immune-deficient mice in terms of providing a model for studies of the invasive and metastatic capability of human breast cancer xenografts. Genetic labelling of human cancer cells with the lacZ gene is described as a specific and highly sensitive method for identification of micrometastases in such a model.