Cancer microbiome study clarifies which tumours host microbes

A comprehensive analysis of more than 16,000 tumours from the Genomics England 100,000 Genomes Project applied a rigorous bio‑informatic pipeline that removed human DNA and screened remaining sequences against curated microbial databases. The study found that most cancer types, including brain, breast and kidney tumours, do not harbour a distinct microbiome beyond background contamination, suggesting earlier reports were likely affected by laboratory DNA from equipment or handlers. By contrast, tumours of the mouth, oesophagus, stomach and bowel consistently contained genuine microbial communities, encompassing bacteria, viruses, fungi, archaea and even the protozoan Trichomonas. The microbial composition varied with tumour location, subtype and mutation burden. Researchers emphasise that distinguishing real microbial signals from contamination required aggressive filtering of multiple human genome references and up‑to‑date microbial reference libraries. These findings could influence future cancer screening, diagnostics and drug‑development strategies by focusing on tumour types that truly host microbes.