Medical researchers have made a surprise anatomical discovery, finding what looks to be a mysterious set of salivary glands hidden inside the human head – which somehow have been missed by scientists for centuries up until now.

This “unknown entity” was identified by accident by doctors in the Netherlands, who were examining prostate cancer patients with an advanced type of scan called PSMA PET/CT. When paired with injections of radioactive glucose, this diagnostic tool highlights tumors in the body.

In this case, however, it showed up something else entirely, nestled in the rear of the nasopharynx, and quite the long-time lurker.

The tubarial glands structure, indicated by blue arrows, alongside other major salivary glands in orange.

“People have three sets of large salivary glands, but not there,” explains radiation oncologist Wouter Vogel from the Netherlands Cancer Institute.

“As far as we knew, the only salivary or mucous glands in the nasopharynx are microscopically small, and up to 1,000 are evenly spread out throughout the mucosa. So, imagine our surprise when we found these.”

Salivary glands are what produce the saliva essential for our digestive system to function, with the bulk of the fluid produced by the three major salivary glands, known as the parotid, submandibular, and sublingual glands.

There are approximately 1,000 minor salivary glands situated throughout the oral cavity and the aerodigestive tract, but these are generally too small to be seen without a microscope.

The discovery made by Vogel’s team is much larger, showing what appears to be a previously overlooked pair of glands – ostensibly the fourth set of major salivary glands – located behind the nose and above the palate, close to the center of the human head.

“The two new areas that lit up turned out to have other characteristics of salivary glands as well,” says the first author of the study, oral surgeon Matthijs Valstar from the University of Amsterdam.

“We call them tubarial glands, referring to their anatomical location [above the torus tubarius].”

These tubarial glands were seen to exist in the PSMA PET/CT scans of all the 100 patients examined in the study. Physical investigations of two cadavers – one male and one female – also showed the mysterious bilateral structure, revealing macroscopically visible draining duct openings towards the nasopharyngeal wall.