4例伴淋巴样间质的微结节性胸腺瘤的临床病理分析

Micronodular thymoma with lymphoid stroma: a clinicopathological study of four cases

目的探讨伴淋巴样间质的微结节性胸腺瘤(MNT)的临床病理特征、诊断及鉴别诊断、治疗和预后。方法对4例MNT的临床病理和免疫组织化学特点进行分析比较,并结合相关文献复习。结果患者年龄5~62岁,平均年龄42岁,中位年龄52岁,男女比例均等(2∶2)。3例患者无临床症状,在体检时发现纵隔占位,1例患者伴有重症肌无力。4例患者均行纵隔肿瘤切除术。4例MNT组织学形态相似,除1例混合有AB型胸腺瘤外,肿瘤由微小上皮样结节构成,结节被丰富的含有明显生发中心的淋巴细胞间质分隔。结节由卵圆形至梭形细胞构成,细胞核卵圆形,无核分裂。免疫组化:结节内的上皮细胞CK、p63、CK19、CK5/6(+);周围淋巴细胞LCA及CD20(+);原位杂交EBER均(-)。结论 MNT是一种非常罕见的胸腺肿瘤,患者无明显症状,特征性的组织形态学并结合免疫组织化学有助于其诊断及鉴别诊断。

Objective To discuss the clinicopathological features,diagnosis and differential diagnosis,treatment and prognosis of micronodular thymoma with lymphoid stroma(MNT).Methods The clinicopathological characteristics and immunohistochemical expression were retrospectively analyzed in four cases of MNT with the review of the literatures.Results The patients were two men and two women(2∶2)aged 5 to 62 years(mean age of 42 years,median age of 52 years).Three patients did not have any symptoms and the tumors were incidental found in physical examination.One patient was associated with myasthenia gravis.Four patients underwent mediastinal tumor resection.All of the cases of MNT had similar histology.The tumor consisted of epithelioid micronodules separated by abundant lymphocytic stroma with prominent germinal centers.The nodules were composed of oval or spindle cells with oval nuclei devoid of mitotic activity.Immunohistochemistry showed that the epithelial cells in the nodule were positive for CK,p63,CK19 and CK5/6;lymphoid cells in the stroma expressed LCA and CD20.Conclusion MNT is a rare thymus tumor.The patients have no obvious symptom.Diagnosis and differential diagnosis should be made in combination with immunohistochemical staining and histologic examination.