Thymic Extranodal Marginal Zone B Cell Lymphoma of Mucosa-Associated Lymphoid Tissue (MALT) Occurs in Patients without History of Autoimmune Disease, and Is Rarely Involved by MALT Lymphoma-Associated Genetic Alterations: Analysis of 6 Cases.
Hwa Jin Cho, Heounjeong Go, Jin Ho Paik, Kyeong Cheon Jung, Chul Woo Kim, Yoon Kyung Jeon. Seoul National University Hospital College of Medicine, Republic of Korea
Background: Primary thymic extranodal marginal zone B cell lymphoma of MALT (MALT lymphoma) is very rare, and about 30 cases have been reported. It has strong association with autoimmune disease such as Sjogren's syndrome, and about 70% of reported cases occurred in those with autoimmune disease with an interval of 2-25 years.
Design: We investigated 6 cases of thymic MALT lymphoma to characterize clinical, histopathological, and molecular features.
Results: Male to female ration was 1:1 and the age ranged from 54 to 69 years. Of note, only one female patient had suffered from systemic lupus erythematosus for 20 years. Another female patient was diagnosed with rheumatoid arthritis 2 years after thymectomy for MALT lymphoma. Most patients had no symptoms related with lymphoma, and the Ann-Arbor stage was low with IA (n=3) and IIA (n=2). One patient was diagnosed with ocular adnexal MALT lymphoma involving both eyelids, 5 months later after thymectomy, and thus suspected to have stage IVA disease. Mediastinal lymph node involvement was pathologically proven in one of four patients. All patients except for one were treated with surgical excision only, and have been followed with no evidence of disease for 3 to 60 months. All tumors characteristically showed variable sized multiple cysts, which were microscopically lined by thymic epithelium infiltrated small B lymphoid cells and plasma cells, equivalent to lymphoepithelial lesions. In all cases, there were reactive lymphoid follicles and the marginal zone and interfollicular area were infiltrated by small lymphocytes, monocytoid cells, and plasma cells. In FISH analysis, MALT1 gene translocation (n=4) and trisomy 18 (n=5) was not observed in any patients, but trisomy 3 was detected in one of the three patients with available results.
Conclusions: Primary thymic MALT lymphoma can arise in patients with no underlying autoimmune disease. Although most patients have favorable prognosis even in the absence of adjuvant treatment after surgical resection, multi-organ involvement can rarely occur. Alleged MALT lymphoma-associated genetic changes seem to be rare in thymic MALT lymphoma.
Wednesday, March 2, 2011 1:00 PM
Poster Session VI # 199, Wednesday Afternoon