Comment on: 'guidelines for the use of cell lines in biomedical research': human-to-human cancer transmission as a laboratory safety concern.

The guidelines for using cell lines in biomedical research, published recently in BJC (Geraghty et al, 2014), include a pioneering safety warning about human-to-human cancer transmission through cancer cells, a route that we will call extracorporeal metastasis (XM). Because XM has been tacitly dismissed as implausible in everyday laboratory practice, if considered at all, we emphasise the warning by reviewing the underlying evidence and preventive measures.