A "fatty apron" in the abdomen helps fuel the spread of ovarian cancer, research suggests.
In 80% of cases, it has spread to this apron, called the omentum, by the time it is diagnosed.
The Nature Medicine research found once ovarian cancer cells reach the omentum, they take it over.
UK experts said the study was important in aiding understanding of ovarian cancer, the fifth most common cancer in women in the UK.
The omentum lies in the upper abdomen near the stomach. It helps support the organs nearby, but it is not essential.
Often, cancer growth in the omentum exceeds the growth of the original ovarian tumour.
The University of Chicago team injected ovarian cancer cells into the abdomen of healthy mice. They reached the omentum within 20 minutes.
They found that protein signals emitted by the omentum attracted the tumour cells. Disturbing these signals reduced this attraction by at least 50%.
Once ovarian cancer cells reach the omentum, they were found to change so they could feed off the fat cells. 
The researchers suggest that a protein known as fatty acid binding protein (FABP4), a fat carrier, could be key to the process and could be a target for treatment.
Tumour cells next to fat cells in the omentum were found to produce high levels of FABP4, while cancer cells far away from fat cells did not.
When the action of FABP4 was blocked, the transfer of nutrients from fat cells to cancer cells was drastically reduced. It also reduced tumour growth and the ability of tumours to generate new blood vessels.
Lead author Ernst Lengyel, professor of obstetrics and gynaecology at the University of Chicago, said: "The cells that make up the omentum contain the biological equivalent of jet fuel.
The researchers suggest fat metabolism may also contribute to other cancers, such as breast, gastric and colon.

Source: BNA