First report on parotid tissue choristomas within and adjacent to TMJ ligaments.

Objective: To report the first examples of ectopic salivary glands of TMJ ligaments & capsules.
Methods and Materials: Nine subjects with chronic TMJ disorders were found incidentally to have ectopic salivary glands (choristomas) within or near damaged TMJ ligaments and capsules. Clinicopathologic characteristics of 12 TMJs are summarized.
Results: The 9 subjects were ages 22-64 years (average = 43.0); 6 were female. Microscopic examination revealed major, almost complete ligament replacement by dense, avascular fibrous scar tissue in all but 1 sample. Chronic inflammatory cells were present in the stroma of 3 samples. A total of 33 lobular, independent salivary structures of variable sizes were embedded in or near ligaments and/or capsules. Half were multiple in the same joint; 13 were bilaterally located in the joints of a single subject, with 8 small glandular lobules in one TMJ. All glands consisted of histologically normal serous acini except 1 which showed a focal lobule of mucus acini and another comprised only of mucus acini. Serial sections showed no connection to parotid glands. Some choristomas showed the aging phenomena of fatty infiltrates (n = 7) and oncocytosis (n = 7). Additionally, 3 of the 12 TMJ samples contained preauricular lymph nodes, with 3 nodes in 1 joint and bilateral involvement in 1 subject. Of the 5 identified nodes, all but one was hyperplastic, with nonspecific inflammatory histiocytosis.
Conclusions: We report, for the first time, independent salivary gland choristomas (n = 33) within the soft tissues of the TMJ (n = 12), with one joint containing 8 such choristomas. All consisted of normal serous tissue except one, a mucus gland. Additionally, a fourth of TMJ surgical samples contained hyperplastic preauricular lymph nodes.
Competing Interests: Declaration of interests None.
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