Sjögren's Disease-Associated Parotid MALT Lymphoma: Diagnostic Pitfall of Ultrasound-Guided Core Needle Biopsy

Sjögren's disease (SD) is a chronic autoimmune disease associated with an increased risk of extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma), particularly in the parotid glands. However, distinguishing benign SD-associated sialadenitis from early lymphoma remains a diagnostic challenge, especially when biopsy samples are limited. We report an elderly woman presenting with progressive bilateral parotid swelling accompanied by xerostomia and xerophthalmia. Serological testing revealed positive anti-SSA and anti-SSB antibodies, hypergammaglobulinemia, and hypocomplementemia, suggesting Sjögren syndrome. Neck ultrasound demonstrated multiple hypoechoic nodules in both parotid glands. Ultrasound-guided core needle biopsy (US-CNB) revealed lymphoepithelial sialadenitis with mixed lymphocytic infiltration suggestive of SD. Subsequent computed tomography demonstrated necrotic lymphadenopathy in the right parapharyngeal space. Surgical excision of the right parotid tumor was therefore performed, and histopathology confirmed extranodal marginal zone B-cell lymphoma (MALT lymphoma). Staging PET-CT revealed multi-site involvement. Following chemotherapy, a complete metabolic response was achieved, and the patient remained in remission during 30 months of follow-up. Careful surveillance is essential in patients with SD due to the increased risk of lymphoma. Repeat biopsy or surgical excision should be considered when imaging and clinical findings are discordant with CNB results.