Four years ago, a team of researchers led by a heavyweight in the field of microbiology made a stunning claim: Cancers have unique microbial signatures that could one day allow tumors to be diagnosed with a blood test. 

https://www.ncbi.nlm.nih.gov/search/research-news/10640/

https://www.wsj.com/health/healthcare/cancer-study-retracted-research-fallout-9573f842