Resident Program - Case of the Month

January 2024 – Presented by Dr. Heather Greene (Mentored by Dr. Chihong Heidi Zhou)

Discussion

Sialadenosis is an uncommon cause of salivary gland enlargement, typically involving the parotid gland. It is usually bilateral and is often associated with an underlying systemic cause, such as diabetes, alcoholism, bulimia, eating disorders, endocrine disorders, or pregnancy.³ It is a nonneoplastic and noninflammatory condition. The most common clinical presentation is chronic, diffuse, bilateral, painless swelling of the parotid glands in a middle-aged patient. It is often bilateral, but few cases with unilateral sialadenosis have been reported as well. Our patient presents with left parotid gland enlargement.

Since the treatment of sialadenosis should be aimed at the correction of the underlying disorder, it is important to distinguish it from other conditions which may appear similar on imaging and/or cytologic evaluation. Ultrasound is often used to evaluate salivary gland masses. On sonographic imaging, sialadenosis does not appear as a mass lesion. Rather, imaging typically demonstrates diffuse glandular enlargement and hyperechogenicity, as seen in the above ultrasound images.⁴ Color Doppler sonographic imaging demonstrates no increase in blood flow to the enlarged parotid gland.⁴ In chronic cases of sialadenosis, fatty infiltration may be seen as well.²

Sialadenosis results from acinar cell hypertrophy. Fine needle aspiration yields cellular smears with predominantly abundant, normal-appearing acinar epithelial cells. The acinar epithelial cells are arranged in clusters, papillae, and glandular patterns. Large numbers of naked nuclei of epithelial cell origin are present in the background. Groups of ductal epithelial cells are very sparsely scattered. Atypical cells or inflammatory cells are characteristically absent. Aspirates of sialadenosis appear similar to normal salivary gland with some exceptions. In sialadenosis, acinar cells are the predominant component and are significantly larger than normal acinar cells. Normal acinar cells are approximately 50 µm in diameter, whereas acinar cells in sialadenosis can measure up to 100 µm.¹

The main differential diagnosis for sialadenosis is acinic cell carcinoma, which is generally not an aggressive malignancy. On FNA, smears prepared from sampling of acinic cell carcinoma are often moderate to highly cellular and composed of a uniform, single cell type with minimal anisonucleosis. The cells have a low nuclear-to-cytoplasmic (n/c) ratios, smooth, rounded nuclei, and indistinct single nucleoli. Characteristically, the cytoplasm is moderate to abundant, microvacuolated, and contains abundant, coarse granules (zymogens highlighted by PAS-D). IHC stains positively for DOG-1 and SOX-10. Cytogenetically, NR4A3 translocations are common. The background is typically “clean,” lacking necrosis, and with only infrequent naked nuclei. Benign ductal elements and mitotic figures are absent. The tumor cells are arranged as flat cell sheets, thick three-dimensional clusters, papillary-like aggregates, and focal acini. In addition, there is an absence of other normal salivary gland elements, such as lobular, grapelike arrangements of acini, ductal epithelium, and interstitial adipose tissue. These are important features that are used to differentiate acinic cell carcinoma from sialadenosis.

Chronic sialadenitis is another important diagnosis to consider in the differential diagnosis of sialadenosis. In chronic sialadenitis, FNA smears are scantly cellular and show predominantly lymphoid elements with scattered, small sheets of ductal cells. There is a paucity of acinar cells. Lymphocytes infiltrating into sheets of ductal cells with lymphoid tangle formations are often noted. Germinal center elements and fragments of fibrous tissue are sometimes present. Sialadenitis differs from sialadenosis in that it demonstrates predominantly lymphocytes and more ductal epithelial cells than acinar cells, whereas sialadenosis demonstrates predominantly acinar cells and no inflammatory infiltrate. The diagnosis of sialadenosis must not be used in cases of salivary gland swelling due to an underlying inflammatory cause, particularly Sjogren's syndrome.

When sialadenosis is diagnosed, treatment of the underlying cause is the initial management option. However, many patients do not respond to conservative treatment options. When the aesthetic outcome to conservative treatment is unacceptable, pharmaceutical and surgical options may be entertained for refractory cases.²

References

1. Cibas ES, Ducatman BS. "Cytology: Diagnostic principles and clinical correlates". Philadelphia, PA: Elsevier; 2021.
2. Davis AB, Hoffman HT. "Management Options for Sialadenosis". Otolaryngol Clin North Am. 2021 Jun;54(3):605-611. doi: 10.1016/j.otc.2021.02.005. PMID: 34024487.
3. Jagtap SV, Aramani SS, Mane A, Bonde V. "Sialosis: Cytomorphological significance in the diagnosis of an uncommon entity". J Cytol. 2017 Jan-Mar;34(1):51-52. doi: 10.4103/0970-9371.197620. PMID: 28182067; PMCID: PMC5259933.
4. Wen Y, Goo HW. "Sonographic and CT findings of sialadenosis in a child with leukemia". Korean J Radiol. 2012 Sep-Oct;13(5):634-6. doi: 10.3348/kjr.2012.13.5.634. Epub 2012 Aug 28. PMID: 22977332; PMCID: PMC3435862.