evidence: Cancer-associated fungi found in different body sites and gene expression signatures. Fungi found to promote tumorigenesis in different body sites (lung, breast, skin, brain, bone, ovary, colon, head-and-neck, stomach) are listed. Fungi that were highly enriched in cancers and may serve as potential prognostic markers are highlighted in red. The presence of Candida in head-and-neck and colon tumors appears to be associated with pro-tumorigenic and cellular adhesion-related gene pathways, whereas in stomach tumors it seems to be involved in inflammatory responses that ultimately lead to poor prognosis. Multiple fungal-bacterial-immune ecologies were detected across tumors. These mycotypes may be promising to predict the survival of patients with cancer [...] Limitations of these studies lie primarily in the sample pools, as majority of the samples the authors collected were not specifically for microbiome studies. Thus, researchers need to carefully eliminate possible contaminants and false-positive fungal DNA, and repeatable results are needed using samples obtained from a germ-free environment. While these studies provide an explicit link between cancer and fungi, more research is needed to understand the underlying mechanisms by which fungi induce inflammation and promote cancer progression. To answer these questions, researchers need to study one type of cancer at a time and use cells and animal models to examine whether fungi drive healthy cells to become cancerous. Once researchers gain a more comprehensive picture of how fungi function in cancer, they may be able to develop antimicrobial therapies or targeted pre- or probiotic therapies that benefit patients with cancer.