B1型胸腺瘤25例临床病理研究

Type B1 thymoma: a clinicopathological study of 25 cases

目的 探讨B1型胸腺瘤的临床病理特征。方法 113例胸腺瘤按WHO(1999)胸腺瘤诊断标准分类 ,对其中 2 5例B1型胸腺瘤运用免疫组织化学标记 (CKAEI/AE3 、CKpan、EMA、vimentin、LCA和CD2 0 )结合临床影像特征和病理组织形态进行研究。结果 B1型胸腺瘤发病年龄 13～ 6 9岁 ,2 5例均伴有重症肌无力 ,其中 17例呈浸润性生长。组织学表现弥漫增生的淋巴细胞内出现小—中等大小散在分布的肿瘤性胸腺皮质上皮细胞 ,细胞多数呈圆形、卵圆形、浆少、染色质细 ,有 /无核仁 ,部分出现纤维组织分割形成不完全性结节 ,并有血管湖、微囊和胸腺髓质分化。免疫组化显示肿瘤细胞表达CK(pan和AE1/AE3)和vimentin ,淋巴细胞表达LCA和CD2 0。结论 B1型胸腺瘤好发于 4 0岁左右的男性重症肌无力患者 ,具有浸润性生长特性 ,是以胸腺皮质上皮细胞为肿瘤成分的低度恶性肿瘤 。

Objective To investigate the clinicopathologic changes of type B1 thymoma. Methods According to WHO classification of thymoma (1999), 113 cases of thymoma were studied, in which 25 cases of type B1 thymoma were examined by light microscopy and immunohistochemical staining for CKs, EMA, vimentin, LCA and CD20. In addition, the clinical and radiological data were reviewed. Results The age of the patients ranged from 20 to 69 years with average 40. The ratio of man to woman was 2.1 : 1. All the patients were accompanied with myasthenia gravis. The invasive growth pattern of the tumor were found in 17 cases, including involvement in lung ( 7 cases), pericardia (10 cases), aorta (4 cases), internal thoracic artery (1 case), anonymous vein (1 case), left superior pulmonary vein (1 case), thyroid gland and sternum (1 case). Histologically, diffuse lymphoid tumor cells appeared with a round or oval shape, thin chromatin, with or without acidophilic nucleolus, and mixed with the neoplastic epitheloid cells. Partial nodular patterns were formed with mesenchymal fibrosis. Vascular lake, microcyst formation and medullary differentiation were seen in the tumors. The epitheloid tumor cells expressed CKs and vimentin, but not EMA. CK positive cells showed a network-like pattern. The lymphoid tumor cells were positive for LCA and CD20. Conclusions Type B1 thymoma always occurs at adults with myasthenia gravis, characterized with a diffuse invasive growth pattern of epitheloid tumors cells in cortical thymus and a low malignant potential. It is necessary that type B1 thymoma should be distinguished from lymphoma of the thymus.