Suster S, Moran C A
Arkadi M. Rywlin Department of Pathology and Laboratory Medicine, Mount Sinai Medical Center, Miami, Florida 33140, USA.
Am J Surg Pathol. 1996 Dec;20(12):1469-80. doi: 10.1097/00000478-199612000-00006.
Thymic epithelial neoplasms are unusual tumors that may span the gamut from clinically benign, well-differentiated lesions (encapsulated thymoma) to overtly malignant, poorly differentiated neoplasms (thymic carcinoma). It has been commonly believed that lesions displaying obvious cytologic features of malignancy (i.e., thymic carcinoma) represent a unique and separate group that is histogenetically distinct from thymoma. We have studied 22 cases of thymic epithelial neoplasms characterized by the admixture of areas displaying conventional features of thymoma with areas showing features of thymic carcinoma. The tumors occurred in six women and 16 men whose ages ranged from 23 to 83 years (median, 53). The lesions presented in eight patients with symptoms of chest discomfort resulting from the involvement of surrounding structures; in 14 patients, they were asymptomatic and discovered incidentally on routine chest radiographs. Histologically, most tumors showed a combination of conventional thymomatous elements with well-differentiated squamous-cell carcinoma (10 cases), followed by thymoma and poorly-differentiated squamous carcinoma (seven cases) and spindle-cell thymoma with poorly-differentiated squamous carcinoma (five cases). Areas of transition between the two different components could be identified in most cases. In five cases, areas showing the features of clear-cell carcinoma could be seen either arising from squamous carcinomatous elements or within the thymomatous component, and in one case transitions between lymphoepithelioma-like carcinoma and anaplastic carcinoma could be observed. Two patients had a history of myasthenia gravis with biopsy-proven thymomas in whom the tumors had been monitored without treatment for 10 and 14 years before the sudden enlargement of the mass. The resected specimens in both patients showed the emergence of a carcinoma arising from a thymoma. The present cases appear to support the existence of a continuum in the spectrum of differentiation between thymoma and thymic carcinoma, suggesting a close histogenetic relationship between these two conditions. Such findings are important not only for our understanding of these tumors but may also play a significant role in the assessment of the biologic behavior and management of these lesions.
胸腺上皮性肿瘤是一类少见的肿瘤，其范围涵盖从临床良性、高分化病变（包膜型胸腺瘤）到明显恶性、低分化肿瘤（胸腺癌）。人们普遍认为，显示出明显恶性细胞学特征的病变（即胸腺癌）代表一个独特且独立的组，在组织发生学上与胸腺瘤不同。我们研究了22例胸腺上皮性肿瘤，其特征是既有表现出胸腺瘤传统特征的区域，又有显示胸腺癌特征的区域。这些肿瘤发生在6名女性和16名男性中，年龄范围为23至83岁（中位数为53岁）。8例患者因周围结构受累出现胸部不适症状；14例患者无症状，在常规胸部X线检查时偶然发现。组织学上，大多数肿瘤表现为传统胸腺瘤成分与高分化鳞状细胞癌的组合（10例），其次是胸腺瘤与低分化鳞状癌（7例）以及梭形细胞胸腺瘤与低分化鳞状癌（5例）。在大多数病例中可以识别出两种不同成分之间的过渡区域。5例病例中，可以看到显示透明细胞癌特征的区域，其要么起源于鳞状癌成分，要么位于胸腺瘤成分内，1例病例中可观察到淋巴上皮瘤样癌与间变性癌之间的转变。2例患者有重症肌无力病史，活检证实为胸腺瘤，在肿块突然增大前，其肿瘤未经治疗已监测10年和14年。两名患者的切除标本均显示胸腺瘤发生了癌变。目前的病例似乎支持胸腺瘤和胸腺癌在分化谱上存在连续性，提示这两种情况之间存在密切的组织发生学关系。这些发现不仅对我们理解这些肿瘤很重要，而且可能在评估这些病变的生物学行为和治疗中发挥重要作用。
