Pathological aspects of malignant and benign thymic disorders.
Pathological aspects of malignant and benign thymic disorders.
复制标题
恶性和良性胸腺疾病的病理学方面。
作者：
H. Müller;A. Marx
世界卫生组织的一个委员会最近定义了区分胸腺上皮肿瘤(TET)的标准，并将其归类为A型、AB型、B1-3型和C型胸腺瘤。由于每种世卫组织类型的术语仍然存在争议，建议除世卫组织分类外还使用其他名称，以便将来的临床病理研究具有可比性。我们认为A型和AB型胸腺瘤(髓样胸腺瘤和混合型胸腺瘤)临床上是良性的，而B1-3型胸腺瘤(主要是皮质和皮质型胸腺瘤和分化良好的胸腺癌)是低度恶性的，而大多数C型胸腺瘤(II类恶性胸腺瘤)是高度恶性的。尚未被世界卫生组织批准的是最近被描述的“胸腺瘤伴伪肉瘤间质”和“胸腺低度化生癌”，分别被认为是良性或低度恶性。重症肌无力(MG)常出现胸腺病理改变。抗乙酰胆碱受体自身抗体的产生源于抗原驱动的免疫反应，这种反应始于胸腺内部，在胸腺内保持不变，但在MG早期就已经扩散到胸腺外部位。副肿瘤性MG仅见于A型、AB型和B1-3型胸腺瘤。异常的Tet微环境触发肿瘤上皮细胞对非耐受性T细胞的选择。只有在将大量原始的、潜在的自身反应性T细胞输出到肿瘤外部位后，胸腺瘤外的T细胞激活才会启动自身免疫过程。重症肌无力发作后的早期手术对于胸腺炎是必要的，以防止自身反应性T细胞从炎症的胸腺大量输出到胸腺外器官，这通常可以缓解MG的症状。在胸腺瘤中，在MG症状出现之前，自身反应性T细胞向肿瘤外部位的‘扩散’已经持续了数月甚至数年。因此，胸腺瘤手术针对的是肿瘤和局部心血管并发症，很少能成功缓解MG的症状。
A WHO committee recently defined criteria for distinguishing between thymic epithelial tumours (TET) and classified them as type A, AB, B1-3 and C thymomas. As the terminology for each WHO type is still controversial, it is recommended to use also other names in addition to the WHO classification to allow comparability of future clinicopathological studies. We consider type A and AB thymomas (medullary and mixed thymomas) clinically benign, whereas type B1-3 thymomas (predominantly cortical and cortical thymomas and well-differentiated thymic carcinomas) are of low-grade malignant potential and most type C thymomas (category II malignant thymomas) are highly malignant. Not yet approved by the WHO are the recently described 'thymoma with pseudosarcomatous stroma' and the 'low-grade metaplastic carcinoma of the thymus', which are considered as benign or low-grade malignant tumours, respectively. Thymic pathology frequently occurs in myasthenia gravis (MG). Production of autoantibodies against the acetylcholine receptor results from an antigen-driven immune reaction that starts inside the thymus, is maintained there but spreads to extrathymic sites already during the early phase of MG. Paraneoplastic MG occurs only in type A, AB and B1-3 thymomas. Abnormal TET microenvironments trigger nontolerogenic T-cell selection by neoplastic epithelial cells. Only after export of substantial numbers of naive, potentially autoreactive T cells to extratumorous sites does T-cell activation outside the thymoma initiate the autoimmune process. Early surgery after onset of MG is essential in thymitis to prevent substantial export of autoreactive T cells from the inflamed thymus to extrathymic organs, and it usually alleviates MG symptoms. In thymoma, 'dissemination' of autoreactive T cells to extratumorous sites has already continued for many months or even years before emergence of symptoms of MG. Therefore, thymoma surgery is aimed against oncological and local cardiovascular complications and rarely succeeds in alleviating symptoms of MG.