evidence: For years, evidence has been mounting that bacteria are linked to cancer, and sometimes even play a crucial part in its progression. Now, researchers have found a similar connection with another type of microorganism: fungi. Tumours of various types of cancer contain different species of microscopic or single-celled fungus, and investigating the species that are present might one day be useful for diagnosing cancer or predicting its course, according to two studies published in Cell on 29 September. "It’s fascinating to look at fungi in the setting of cancer," says Ami Bhatt, a microbiome specialist at Stanford University in California. But she cautions that the studies only suggest that there is an association between fungal species and certain cancers—they do not show whether or not the fungi are directly responsible for cancer progression. [...] Although this research provides the clearest link yet between cancer and fungi, Saxena says more work is needed to understand whether fungi can contribute to cancer progression by causing inflammation, for example, or if advanced tumours create a habitable environment that encourages fungal cells to take hold.