Levine G D, Rosai J
Hum Pathol. 1978 Sep;9(5):495-515. doi: 10.1016/s0046-8177(78)80131-2.
Although the term thymic hyperplasia is used most commonly to indicate the occurrence of germinal centers in the thymus, cognizance must be taken of the fact that such centers may occur in apparently normal thymuses in both children and adults. A concept of thymic compartmentalization is proposed with origin of germinal centers in the perivascular space (extraparenchymal compartment) of the thymus. These germinal centers contain a high percentage of B lymphocytes in contrast to the true thymic parenchyma. Although the significance of germinal centers in the thymus parenchyma. Although the significance of germinal centers in the thymus in myasthenia gravis remains controversial, removal of nonneoplastic thymus in this condition is of proven therapeutic value. A variety of neoplasms originating in the thymus have previously been lumped together under the single term "thymoma." It is apparent, however, that thymoma, thymic carcinoid, various lymphomas, and germ cell tumors that arise in the thymus differ not only pathologically but also in their clinical behavior. Thymoma is regarded as an epithelial neoplasm and ultrastucturally is characterized by many desmosomes and tonofilaments. The lymphocytes do not behave in a malignant manner, and lymphomas of the thymus should be sharply separated from true thymoma. Poorly differentiated thymic carcinoma and histiocytic lymphoma may be distinguishable only by the electron microscopic demonstration of desmosomes and filaments in the thymic carcinoma. The evidence that Hodgkin's disease of the thymus ("granulomatous thymoma") is not a variant of thymoma appears overwhelming. Lymphoblastic lymphoma of the thymus is a distinctive neoplasm that is especially prevalent in teenage males. High levels of terminal transferase characterize the lymphoblasts and there is a striking tendency for leukemia to occur. Thymic carcinoid is usually nonfunctional, although one-third of the reported cases are associated with Cushing's syndrome. On light microscopy a ribbon pattern and punctate necroses are characteristic of thymic carcinoids. Electron microscopic demonstration of many dense core granules is invaluable in establishing this diagnosis. An important clue to the diagnosis of thymic seminoma (a neoplasm that shows the same radiosensitivity as its testicular counterpart) is the frequent presence of epithelioid and giant cell granulomas and germinal centers. Separation of the various thymic neoplasms described not only is justifiable on pathologic grounds but is often essential for appropriate patient investigation and treatment.
虽然术语“胸腺增生”最常用于指胸腺生发中心的出现，但必须认识到这样的生发中心可能出现在儿童和成人看似正常的胸腺中。本文提出了胸腺分区的概念，生发中心起源于胸腺的血管周围间隙（实质外区）。与真正的胸腺实质相比，这些生发中心含有高比例的B淋巴细胞。虽然胸腺实质中生发中心的意义。虽然重症肌无力患者胸腺中生发中心的意义仍存在争议，但在这种情况下切除非肿瘤性胸腺具有已证实的治疗价值。以前，起源于胸腺的各种肿瘤都被归在“胸腺瘤”这一单一术语之下。然而，很明显，胸腺瘤与胸腺类癌以及胸腺中出现的各种淋巴瘤和生殖细胞肿瘤不仅在病理上不同，而且在临床行为上也不同。胸腺瘤被视为一种上皮性肿瘤，超微结构上其特征是有许多桥粒和张力丝。淋巴细胞不表现出恶性行为，胸腺淋巴瘤应与真正的胸腺瘤严格区分。低分化胸腺癌和组织细胞淋巴瘤可能仅通过电镜下胸腺癌中桥粒和细丝的显示才能区分。胸腺霍奇金病（“肉芽肿性胸腺瘤”）不是胸腺瘤的一种变体，这一证据似乎非常确凿。胸腺淋巴母细胞淋巴瘤是一种独特的肿瘤，在青少年男性中尤为常见。淋巴母细胞具有高水平的末端转移酶，并且有明显的白血病发生倾向。胸腺类癌通常无功能，尽管三分之一的报告病例与库欣综合征有关。在光学显微镜下，带状模式和点状坏死是胸腺类癌的特征。电镜下显示许多致密核心颗粒对于确立这一诊断非常重要。胸腺精原细胞瘤（一种与睾丸精原细胞瘤具有相同放射敏感性的肿瘤）诊断的一个重要线索是经常出现上皮样和巨细胞肉芽肿以及生发中心。区分上述各种胸腺肿瘤不仅在病理学上是合理的，而且对于患者的适当检查和治疗往往至关重要。
