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B-cell marginal zone lymphoma in a parotid gland lympho-epithelial cyst occurring in a patient diagnosed with clonal B-cell lymphocytosis: a case report

ABSTRACT
A patient with a history of CD5-negative and CD23-negative clonal B-cell lymphocytosis presented at the Department of Maxillofacial surgery of Luigi Vanvitelli University of Naples for a nodule in the deeper left parotid region, discovered accidentally during a follow-up for the lymphocytosis. Ultrasounds and magnetic resonance imaging showed multiple nodules, the biggest of about 1.5 centimeters, partly solid and partly cystic. US-guided fine needle aspiration cytology and flow cytometry were executed. Flow cytometry evaluation showed a CD19+, CD10-, CD23-, CD5- cellular population with restriction for kappa chain.
Final diagnosis of a monoclonal B-cell lymphoproliferative disorder was rendered, and the patient underwent to partial left parotidectomy. Histological examination showed lymphoid nodules with some cysts in the context. The lymphoid cell population resulted positive for BCL-2 and partially positive for CD43. The immunohistochemical determination for CD23 showed the presence of irregular-shaped residual networks of follicular dendritic cells, and images of follicular “colonization” by small, BCL-2- positive and CD2-negative lymphoid cells. Proliferation index (Ki67) resulted about 10%. The fluorescence in-situ hybridization (FISH) did not show IGH rearrangement. Finally, polymerase chain reaction (PCR) was performed for clonality assessment and showed the clonal IG heavy V-D-J (IGH) gene rearrangement. A final diagnosis of an extranodal non-Hodgkin B-cell marginal zone lymphoma (MZL) occurring in the context of a lympho-epithelial cyst was rendered.

IMPACT STATEMENT
Exceptionally rare case of an extra-nodal B-cell marginal zone lymphoma arising in the context of a lympho-epithelial cyst of the parotid gland, in a patient affected by clonal peripheral lymphocytosis.

Table of Content: Vol. 4 (No. 2) 2024 June

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