By comparison, the skin - until now considered to be the largest human organ - only holds about 16 percent of the body mass.
Researchers found the web-like tissue on the underside of skin, around the digestive tract, bladder, lungs, arteries, and within muscles.
In a news release, they also noted that the organ acts as a sort of "shock absorber" that protects the body's tissues from tearing, "as organs, muscles, and vessels squeeze, pump, and pulse as part of daily function". Knowing what to look for, they quickly found the watery chambers around other tissues and organs in the body.
The new organ was first identified by Dr. David Carr-Locke and Dr. Petros Benias from the Mount Sinai Beth Israel Medical Center. However, "While the anatomy and composition of the interstitial space between cells is increasingly understood, the existence, location, and structure of larger inter- and intra-tissue spaces is described only vaguely in the literature".
"Once they get in, it's like a water slide". The tissue contains interconnected, fluid-filled spaces that are supported by a lattice of thick collagen "bundles", Theise said. At the time, the mesh-like cavities appear alien to them. It's ideal to catch the mutated cells before they reach the lymph nodes, but some types of cancer, such as urinary cancer, are not possible to screen. And not all experts are sure that it is accurate to call the interstitium an organ. Jennifer Munson, a biomedical engineer at Virginia Tech tells Sarah Gibbens of National Geographic that while the new paper demonstrates "the benefit of having new ways to image and look at tissues", further research into the interstitium's function is warranted. Cancer cells can penetrate these channels and thus directly find themselves in the lymphatic system.
Researchers discovered the interstitium by using a novel medical technology - Probe-based confocal laser endomicroscopy.
Despite its size and widespread presence in the human body, the interstitium has been overlooked in anatomical studies until now due to the procedure previously used by researchers to analyze tissue.
This is the second time in as many years humans have learned details about a new organ.
Now, a team from New York University's School of Medicine, is asking for a re-think of the "previously unappreciated" tissue layers of the interstitium. He contends that it is important to know whether interstitium is an effect or cause of cancer.
Theise wrote that the discovery of the organ could lead to new ways of detecting cancer or other diseases.
Dr Theise said: "The more tissues I saw, the more I realized it's everywhere".
'This includes the possibility that the direct sampling of interstitial fluid may become a powerful diagnostic tool.