110 - Human Tubarial Glands Are Minor Salivary Glands

Poster Board Number: 110
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Abstract Body : Background: There are three pairs of major salivary glands (SGs) and around 1000 minor SGs spread throughout the human aerodigestive tract. Traditionally, major SGs have been distinguished from minor SGs based on their larger size, complex acinar-duct branching, and recognizability on standard radiographic images. The tubarial glands (TGs) are a collection of SGs located bilaterally within the nasopharynx, proximal to the Eustachian tube. In cancer patients, the TGs displayed a distinct region of prostate specific membrane antigen (PSMA)-ligand uptake in the nasopharynx with similar intensity of uptake to the major SGs, leading to their classification as major SGs by Valstar et al. (Radiotherapy Oncology 2021 vol.154 p.292-8). Currently, there has been no inclusive quantitative characterization of the anatomical structure of the TGs. This study investigated the histological similarities and differences between the TGs and the major and minor SGs, and to characterize any sexual dimorphism in the TGs.
Methods: Parotid (PG), submandibular (SM), sublingual (SL), buccal (Buc), labial (Lab) and lingual (Lin) glands were excised from 9 male and 3 female human cadavers. Hematoxylin and eosin-stained tissue sections were visualized using light microscopy. Complexity, branching, lobule size, acini area and duct density were analyzed using ImageJ software. Statistical analysis was conducted using a two-tailed unpaired t-test with a significant p-value of 0.05. This study received approval from the University of Calgary Conjoint Health Research Ethics Board.

Results: TGs are comprised of densely packed clusters of seromucous acini surrounded by loose connective tissue similar to minor SGs, and have ducts running parallel to the mucosal surface of the nasopharynx, as is seen in the major SGs. The average total glandular area occupied by TGs in one 10x magnification field was comparable to the minor SGs. There was no significant difference between the duct density of the glands or between males and females. Duct densities (male and female combined) were as follows: TG=0.036, PG=0.041, SM=0.058, SL=0.052, Buc=0.061, Lab=0.057, Lin=0.049.

Conclusions: TGs share morphology similar to minor SGs. Qualitatively, TGs contain acini arrangements and duct densities that more closely reflect the minor SGs than the major SGs. Quantitatively, there is no distinction between the duct densities of the major and minor SGs. This indicates that the SGs might lie along a spectrum, instead of being categorized into two distinct groups. Ordering the glands along a spectrum would account for these similarities and would potentially explain why the TGs were reported by Valstar et al. to have a similar PSMA-ligand uptake to the major SGs while histologically having many similarities to the minor SGs. Other parameters that were not considered were the size and duct branching structure of each gland, which would likely provide a clearer distinction between major and minor SGs.