Primary Cutaneous Marginal Zone B-Cell Lymphoma Complicating Long-Standing Primary Sjögren’s Syndrome – A Multidisciplinary Diagnostic Challenge

Primary Sjögren’s syndrome is a chronic autoimmune exocrinopathy associated with a significantly increased risk of developing Non-Hodgkin lymphoma, particularly extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue. Primary cutaneous marginal zone B-cell lymphoma represents a rare, indolent subtype of primary cutaneous Non-Hodgkin lymphoma that may occur in the setting of autoimmune diseases, and its association with primary Sjögren’s syndrome has become an area of growing scientific interest. We present the case of a female patient with a 10-year history of primary Sjögren’s syndrome treated with chloroquine therapy since 1999, who developed erythematous plaques on the trunk in January 2024. Following unsuccessful local corticosteroid therapy and extensive diagnostic evaluation including two consecutive skin biopsies with immunohistochemical analysis, Primary cutaneous marginal zone B-cell lymphoma was diagnosed (CD20+, CD79a+, Bcl-2+, CD43+/−, Ki-67 ~5%). Bone marrow biopsy and multislice computed tomography of the chest, abdomen, and pelvis showed no evidence of systemic involvement. The diagnosis was established through a multidisciplinary collaboration between dermatologists, rheumatologists, and hematologists. This case highlights the importance of considering lymphoproliferative disorders in patients with primary Sjögren’s syndrome who develop persistent skin lesions. A multidisciplinary approach, timely re-biopsy, and comprehensive immunohistochemical analysis are essential for establishing an accurate diagnosis and ensuring appropriate management of this rare but clinically significant association between two diseases.