胸腺原发黏膜相关淋巴组织淋巴瘤及淋巴上皮性涎腺炎样胸腺增生的临床病理分析

目的探讨胸腺原发黏膜相关淋巴组织(mucosa associated lymphoid tissue,MALT)淋巴瘤和淋巴上皮性涎腺炎(lymphoepithelial sialadenitis,LESA)样胸腺增生的临床病理学特征、两者相关性及鉴别诊断。方法分析3例胸腺MALT淋巴瘤和1例LESA样胸腺增生的临床病理学和免疫表型特征,并复习相关文献。结果 3例胸腺MALT淋巴瘤,其中2例伴Sj9gren综合征;镜下胸腺正常结构损毁,增生的淋巴滤泡间可见肿瘤性淋巴样细胞浸润伴明显的淋巴上皮病变,以中心细胞样和单核样B细胞形态为主。瘤细胞表达CD20、PAX-5和BCL-2,其中1例伴显著浆细胞分化者Lambda轻链限制性表达。3例胸腺MALT淋巴瘤免疫球蛋白(immunoglobulin,Ig)基因检测均示单克隆性重排。LESA样胸腺增生镜下胸腺分叶状结构大体尚存,可见包含增生滤泡的丰富淋巴细胞浸润,胸腺上皮增生伴显著淋巴上皮病变,未见有单核样B细胞形态。免疫组化染色示增生淋巴组织由B和T细胞混合;Ig基因重排检测示多克隆性增生。结论 LESA样胸腺增生和胸腺MALT淋巴瘤均是胸腺少见的淋巴增生性病变,两者具有相似的组织学和免疫表型特征;结合基因重排技术详细分析两者的鉴别要点,有助于鉴别。

Clinicopathologic study of primary thymic extranodal marginal zone lymphoma of mucosa associated lymphoid tissue and lymphoepithelial sialadenitis-like thymic hyperplasia

Purpose To discuss the clinicopathological features of primary thymic extranodal marginal zone lymphoma of mucosa associated lymphoid tissue (MALT) lymphoma and lymphoepithelial sialadenitis (LESA)-like thymic hyperplasia,their relationship and differential diagnosis.Methods Three cases of thymic MALT lymphoma and one LESA-like thymic hyperplasia were evaluated by HE staining,immunohistochemistry and immunoglobulin (Ig) gene rearrangement technology.Results The symptoms of Sjsgren syndrome were found in the two patients with thymic MALT lymphoma.Microscopically,the normal architecture of thymus was effaced by dense lymphoid infiltration composed predominantly of centrocyte-like and monocytoid B cells with prominent lymphoepithelial lesions.Immunohistochemically,the tumor cells were positive CD20,PAX-5,and BCL-2.The plasma cells showed lambda light chain restriction in one case with prominent plasmacytoid differentiation.In LESA-like thymic hyperplasia,the normal lobular architecture of thymus was generally reserved and abundant lymphoid tissue containing lymphoid follicles was seen with prominent lymphoepithelial lesions in expanding islands of thymic epithelial cells and epithelium lining the cysts,but a monocytoid B-cell population was absent.Immunohistochemically,a mixed B-cell and T-cell population was identified.A monoclonal rearrangement of the Ig gene was detected in all three thymic MALT lymphomas but not in the case of LESA-like hyperplasia.Conclusion Primary thymic MALT lymphoma and LESA-like thymic hyperplasia are both rare lymphoid proliferative lesions and the two lesions have overlapping histological and immunohistochemical features.A combination of genetic rearrangement and analysis of the differential points is helpful to distinguish between them.