The organ is a body-wide network of interconnected, fluid-filled compartments.
The study published Tuesday in Scientific Reports suggests this organ, called the interstitium, is a series of interconnected, fluid-filled compartments found throughout the body.
The interstitium was previously thought to be dense layers of connective tissue, but it turns out that it is actually one of the largest organs in the human body - and understanding it better may offer clues to understanding how cancer spreads.
The organ is made up of a group of tissues in a living organism that have been adapted to perform a specific function.
Scientists have long known about the body's various interstitial spaces between cells, but its importance was never quite understood.
Dr. Benias and colleagues found that the removal of fluid as slides are made causes the connective protein meshwork surrounding once fluid-filled compartments to pancake, like the floors of a collapsed building.
The NYU-led team says the newly discovered organ is found all over the body - but somehow, it hasn't been identified until now. This network of channels is present throughout the body and works as a soft, elastic cushion, protecting the organs from external shocks as the body moves. Upon further scrutiny, they determined that the lattice is composed of collagen bundles that support fluid-filled spaces and are lined irregularly with flattened cells that produce two markers, one endothelial and one mesenchymal.
The finding may help decipher how cancer travels to lymph nodes; if the malignant cells cross over into the interstitium, they are on a direct path to the lymph nodes because that fluid drains into the lymphatic system.
Interstitium has both, he explained.
More research is likely to be needed to find out whether this improved understanding of the interstitium can be used to fight disease.
Such spaces, underpinned by a mesh of solid yet flexible connective tissue proteins, can function as shock absorbers that can thwart tissues from tearing on account of muscles, organs, and vessels squeezing and pumping to complete their daily functions.
Scientists believe that the organ was missed because of the way tissue is studied. The researchers collect tissues using a technology called confocal laser.
Researchers collected tissues samples of bile ducts from 12 cancer patients during surgery. Such examination is described as "in vivo", meaning it takes place inside a living organism, rather than on dead tissue on a slide.
Cancer can spread through the lymphatic system, so the researchers wanted to see if cancer cells might also spread into the interstitium.
For this study the team looked at the interstitium using a powerful microscope using confocal laser endomicroscopy wherein the tissue samples are bathed in a fluorescent liquid to delineate their structure in minute details.
"Can we detect [disease] earlier by sampling fluid from the space?".
This fluid layer that surrounds most organs may explain why cancer spreads so easily.
On a fundamental level, it says, "our findings necessitate reconsideration of numerous normal functional activities of different organs and of disordered fluid dynamics in the setting of disease, including fibrosis and metastasis" - that is, the spread of cancer.