Interstitium, the new organ, was based on the original paper quoted by the OP above. The article was published March 27, 2018.
E.g. Relevant quotes:
"and as a result propose a large-scale revision of the macro- and microanatomy of the human interstitium."
"In sum, we describe the anatomy and histology of a previously unrecognized, though widespread, macroscopic, fluid-filled space within and between tissues, a novel expansion and specification of the concept of the human interstitium."
Last time a new organ was discovered was around Christmas time (more than a year ago - see previous post). This time it happened around Easter time. It seems, either way, we get an organ as a gift! ...