For decades, immortal cells such as the famous HeLa cells have been contaminating other cell cultures in the lab.
Scientific journal PLOS ONE will publish the results on 12 October.
HeLa was named after Henrietta Lacks, the woman whose cervical cancer cells were biopsied and used for medical research.
HeLa cells were thrust into the public eye in recent years thanks to the book and the made-for-TV film of the same name The Immortal Life of Henrietta Lacks.
This wasn't limited to HeLa alone, but was also observed in other immortal cell lines.
Biomedical researchers may think they're working with human cancer cells, when in fact the majority have been taken over by mouse cells.