[Clinicopathologic features of primary thymic extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue type].
OBJECTIVE
To study the clinicopathologic features of primary thymic extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT).


METHODS
The clinical and pathologic findings were evaluated in 3 cases of biopsy confirmed thymic MALT lymphoma. The clincopathologic features, treatment and prognosis were discussed and literatures reviewed.


RESULTS
One male and two female patients presented with asymptomatic mediastinal masses with a history of Sjögren syndrome. They were aged 36, 35 and 41 years respectively, and only one patient had B symptoms. Grossly, all three tumors were encapsulated and had multiple variable-sized cysts on cut-surface. Histopathologically, the normal thymic lobular architecture was effaced by abnormal dense lymphoid infiltration. Prominent lymphoepithelial lesions were formed by centrocyte-like cells infiltrating and expanding Hassall's corpuscles and epithelial cyst lining. All cases showed apparent plasmacytic differentiation. Immunohistochemically, the tumor cells were positive for CD20, CD79a, bcl-2 and negative for CD3, CD5, cyclin D1, CD43, CD10, bcl-6, and CD23. The plasma cells showed kappa light chain restriction. Immunoglobulin heavy chain rearrangement in three cases was confirmed by PCR. All patients were at early stage and received routine chemotherapy with or without radiotherapy after surgical removal. All patients achieved complete remission with 24, 18 and 3 months follow-up, respectively.


CONCLUSIONS
Primary thymic MALT lymphoma may be a rare distinctive lymphoma. It can be diagnosed by HE and immunohistochemical study and should be differentiated from reactive lymphoid proliferation, other types of lymphoma and mediastinal thymoma.
Department of Pathology, General Hospital of People's Liberation Army, Beijing 100853, China.
Lu
L
Sun
Huai-yin
HY
Shi
Li-xin
LX
Wei
D000328:Adult; D058846:Antibodies, Monoclonal, Murine-Derived / Q000627:therapeutic use; D018951:Antigens, CD20 / Q000378:metabolism; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D003520:Cyclophosphamide / Q000627:therapeutic use; D003937:Diagnosis, Differential; D004317:Doxorubicin / Q000627:therapeutic use; D005260:Female; D005500:Follow-Up Studies; D015326:Gene Rearrangement, B-Lymphocyte, Heavy Chain; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000235:genetics; D053539:Keratin-19 / Q000378:metabolism; D018442:Lymphoma, B-Cell, Marginal Zone / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism / Q000473:pathology* / Q000601:surgery; D008297:Male; D011241:Prednisone / Q000627:therapeutic use; D019310:Pseudolymphoma / Q000473:pathology; D000069283:Rituximab; D013952:Thymus Hyperplasia / Q000473:pathology; D013953:Thymus Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism / Q000473:pathology* / Q000601:surgery; D014750:Vincristine / Q000627:therapeutic use
D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20; D007143:Immunoglobulin Heavy Chains; D053539:Keratin-19; C571759:R-CHOP protocol; D000069283:Rituximab; D014750:Vincristine; D004317:Doxorubicin; D003520:Cyclophosphamide; D011241:Prednisone