salivary glands tubarial glands human anatomy
salivary glands tubarial glands human anatomy

Scientists Question Discovery of New Human Salivary Gland

A widely publicized paper has drawn scrutiny from physicians and anatomists about the authors’ claims regarding so-called tubarial glands.  

Diana Kwon
Diana Kwon

Diana is a freelance science journalist who covers the life sciences, health, and academic life. She’s a regular contributor to The Scientist and her work has appeared in several other...

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Jan 12, 2021

ABOVE: A 3-D reconstruction from histological slides (inset on right) of the newly discovered tubarial gland (yellow; ducts in light blue). The torus tubarius cartilage is colored dark blue and muscle is pink.
M. Valstar et al., Radiotherapy & Oncology, doi:10.1016/j.radonc.2020.09.034, 2020.  

Last year, a paper reporting the discovery of a pair of salivary glands made headlines at numerous publications, including The Scientist. That manuscript, which was published in Radiotherapy & Oncology, has since received criticism from several groups of scientists who question the authors’ claims. To date, at least eight letters to the editor have been submitted to the journal in response to the paper.

“I don’t think the paper should be retracted, it should just be corrected,” says Daniel Cohen Goldemberg, an oral pathologist at the National Cancer Institute of Brazil and an author of one of the letters. “It’s a good paper, it’s just not focusing on what it should be.”

In the paper, a group of researchers from the Netherlands describe a pair of salivary glands dubbed “tubarial glands” for their location in the torus tubarius, a section in the nasopharynx—the upper portion of the throat. These findings were based on the team’s examinations of scans from 100 cancer patients, dissections of two human cadavers, and imaging in one healthy volunteer. After finding that exposure to radiotherapy was associated with dry mouth and swallowing difficulties in a previously collected dataset of more than 700 head and neck cancer patients, they noted that these glands may be at risk for damage from this treatment.

See “Scientists Discover New Human Salivary Glands

Multiple issues were raised in the letters sent to the journal, but one of the most common included questions about the novelty of the Dutch team’s finding. One letter pointed out, for example, that the existence of a structure fitting the description of the tubarial glands has been around since the 19th century. Others questioned whether it was appropriate to classify this structure as a salivary gland at all. Some scientists noted that due to issues such as the location of the glands, which suggests that their fluids do not reach the mouth and that they are therefore not involved in the production of saliva, and the glands’ apparent lack of amylase, a key protein found in saliva, it was not appropriate to classify the tubarial glands as salivary glands.

“The study would have been better if it had focused on the [importance for radiotherapy] instead of trying to create this supposed new gland, because there is no new gland,” says Cohen Goldemberg. “If I had been a reviewer [of the paper], I would probably not have rejected it, but I would surely not accept it as-is.”

In another letter, the authors pointed out all but one of the 100 patients in the sample used to identify the tubarial glands were male. Because of this gender imbalance, the authors note that it will be important to conduct further analyses to determine if are any differences in these structures in females.

Reports of new discoveries in human anatomy are rare—and often fraught with debate. Other recent claims of previously unknown bits of human anatomy, such as the mesentery, a fan-like sheet of tissue holding the intestines together, and the interstitium, a network of fluid-filled spaces between cells, have also been questioned.

Albert Mudry, an otorhinolaryngology specialist and adjunct professor at Stanford University who coauthored one the letters in response to the tubarial glands paper, says that he is skeptical about any paper that claims to have discovered something completely novel—whether that’s a new organ or a new scientific technique—because authors often fail to conduct a thorough scan of past literature to verify the novelty. The authors of the tubarial glands paper “use a different anatomical term, but [the structure] was already described many years before and many times before.” Mudry’s letter points out that in the 19th century, anatomists Jean Cruveilhier and Jakob Henle and otologist Adam Politzer described glands in this region of the throat.

See “New Discoveries in Human Anatomy

The authors stand by their claims. In a response letter, they comment on the criticisms, stating, among other things, that evidence from their study does not rule out the possibly that fluids from the tubarial glands reach the mouth or that amylase is present. They also note that while there have been descriptions of such structures in the past, their study provides a new perspective on prior observations.

“We’ve conducted an extensive study, but obviously there are a lot of ways you can see it, or things that we missed,” says Matthijs Valstar, an oral and maxillofacial surgeon at the Netherlands Cancer Institute (NKI) and a coauthor of the original study. He adds that there were a number of nuances about the findings mentioned in the paper—such as the acknowledgement that there might be disagreement about whether the tubarial glands were major or minor glands and whether they could be considered separate organs—that he thinks some of the letters did not acknowledge.

Wouter Vogel, a radiation oncologist at the NKI and another coauthor of the tubarial gland study, says he and his colleagues welcome the comments, as they provide avenues for further research. “Some of the authors of the letters were not yet comfortable with declaring these newly discovered glands . . . [and said] that they would like to see additional evidence, and also made very valid suggestions,” Vogel tells The Scientist. “This actually really helps us to explore further and to build more evidence. Of course, then it’s a matter of opinion, how much evidence you need to name something as a gland.”