Scientists discovered traces of fungi lurking in the tumors of people with different types of cancer, including breast, colon, pancreatic, and lung cancers.

In one study, researchers dusted for the genetic fingerprints of fungi in 35 different cancer types by examining more than 17,000 tissue, blood, and plasma samples from cancer patients.

Not every single tumor tissue sample tested positive for fungus, but overall, the team did find fungi in all 35 cancer types assessed.

"Some tumors had no fungi at all, and some had a huge amount of fungi," co-senior author Ravid Straussman, a cancer biologist at the Weizmann Institute of Science in Rehovot, Israel, told STAT; often, though, when tumors contained fungi they did so in "low abundances," the team noted in their report.

Based on the amount of fungal DNA his team uncovered, Straussman estimated that some tumors contain one fungal cell for every 1,000 to 10,000 cancer cells.

The studies also don't address if fungi can contribute to cancer development, pushing healthy cells to turn cancerous.