Correct answer to Q3 is: Ultrasound-guided core needle biopsy
 A. Color Doppler ultrasound shows some vascularity in the gland  B. Ultrasound-guided core biopsy of the right parotid gland.  C. Pathological examination of the specimen.
Discussion:
Pathological examination showed cores of salivary gland tissue with acinar atrophy, interstitial fibrosis, admixed plasma cells and patchy infiltrates of small lymphocytes without prominent nuclear atypia. Immunohistochemistry and the highest density of IgG4 and IgG positive cells were counted. There were more than 100 IgG4 (+) cells per high-power field, and the percentage of
IgG4 (+)/IgG (+) cells were more than 40%. The morphologic and immunophenotypic features suggested a diagnosis of IgG4-RD sialadenitis.
The patient had Sicca syndrome clinically with manifestation of dry eyes and dry mouth for more than one year before the ultrasound-guided intervention. However, Sjögren syndrome was excluded because the serological test for anti-Ro/SSA antibodies and anti-La/SSB antibodies was negative.
IgG4-RD is a chronic immune-mediated disorder characterized by the infiltration of affected organs with abundant IgG4-positive plasma cells as shown in this case. It often follows a chronic, relapsing, and frequently asymptomatic course, making diagnosis challenging. The disease can involve multiple organs and may present as tumor-like masses, commonly affecting the pancreas, bile ducts, lacrimal glands, orbital tissues, salivary glands, lungs, kidneys, retroperitoneal tissues, aorta, meninges, and thyroid gland.
Outside the pancreato-biliary system, the head and neck are major sites of IgG4-RD involvement. The salivary gland is frequently affected, accounting for approximately 25.9% of extra-pancreatic lesions. The elevated serum IgG4 levels, observed in up to 75% of cases, was also found in this case. Sonographic findings of IgG4-RD in the parotid gland typically show multiple small hypoechoic nodules within a relatively hyperechoic background, as demonstrated in this case.
When active therapeutic intervention is needed, corticosteroids are the first-line treatment. Most patients with IgG4-RD show rapid clinical improvement after steroid administration.
Conclusion
Beside the pancreatico-biliary glands, the head and neck are the most common regions for IgG4-RD. When active therapeutic intervention is needed, most patients show rapid recovery after administration of steroid.
Conflicts of interest
“The authors declare no conflict of interest.”
References
- Wu PH, Chang YC, Liao LJ. IgG4-Related Disease Presenting as Cervical Lymphadenopathy. J Med Ultrasound. 2018; 27: 43-46.
- Wan YL, Chan SC, Chen YL, et al. Ultrasonography-Guided Core Needle Biopsy of Parotid Gland Masses. AJNR Am J Neuroradiol. 2004; 25:1608-1612.
- Lorenzon M, Spina E, Tulipano F, et al. Salivary Gland Ultrasound in Primary Sjögren’s Syndrome: Current and Future Perspectives. Open Access Rheumatol. 2022; 14: 147-160.
- Czarnywojtek A, Agaimy A, Pietrończyk K, et al. IgG4-Related Disease: An Update on Pathology and Diagnostic Criteria with A Focus on Salivary Gland Manifestations. Virchows Arch. 2024; 484: 381-399
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