Just when it was thought we had a good understanding of the human body, new research makes it clear we do not.

Researchers at New York and Philadelphia have proposed the interstitial fluid that surrounds much of our internal organs is more complex and integrated than we thought and that it should be considered an organ as well. Their study, published March 27, 2018 in Scientific Reports shows that the connective tissue and fluids that fill in the spaces in our body are similar in structure throughout the body and may provide valuable insight into how some diseases progress (i.e., cancer).

This organ was largely invisible to us in the past due to the way researchers normally fix tissue for viewing under the microscope. However, using a new staining and freezing technique, the researchers were able to see the interstitial layers in all their complexity and that their fluid filled spaces are an integral part of the body.

new organ

In a press release, lead author Neil D. Theise, MD, of NYU Langone Health said, “This finding has potential to drive dramatic advances in medicine, including the possibility that the direct sampling of interstitial fluid may become a powerful diagnostic tool.”

In their discussion of the report, the authors noted that “while typical descriptions of the interstitium suggest spaces between cells, we describe macroscopically visible spaces within tissues – dynamically compressible and distensible sinuses through which interstitial fluid flows around the body. Our findings necessitate reconsideration of many of the normal functional activities of different organs and of disordered fluid dynamics in the setting of disease, including fibrosis and metastasis.”

The more you know.


Benias PC, Wells RG, Sackey-Aboagye B, et al. Structure and distribution of an unrecognized interstitium in human tissue. Scientific Reports. 2018;8:4947. doi:10.1038/s41598-018-23062-6.


Images obtained from Benias et al 2018, an open-source publication.