Many cell lines that are widely used for biomedical research have been overgrown by other, more aggressive cells. For example, supposed thyroid lines were actually melanoma cells, supposed prostate tissue was actually bladder cancer, and supposed normal uterine cultures were actually breast cancer. This is a list of cell lines that have been cross-contaminated and overgrown by other cells. Estimates based on screening of leukemia-lymphoma cell lines suggest that about 15% of these cell lines are not representative of what they are usually assumed to be. A project is currently underway to enumerate and rename contaminated cell lines to avoid errors in research caused by misattribution.