Wang Zheng, Zong Wenkang, Liang Shuo, Sun Daqiang
Department of Thoracic Surgery, Tianjin Chest Hospital, Tianjin, China.
Department of Pathology, Tianjin Chest Hospital, Tianjin, China.
AME Case Rep. 2024 May 30;8:64. doi: 10.21037/acr-23-213. eCollection 2024.
Metaplastic thymoma (MT), an exceedingly rare variant of primary thymic epithelial neoplasms, is distinguished by its indolent progression and unique histopathological profile. It presents a biphasic pattern characterized by solid epithelial and spindle cell components, potentially leading to diagnostic confusion with type A thymomas or the type A component of type AB thymomas. Accurate diagnosis is pivotal for optimal therapeutic strategies and prognostication.
We document an exceptional case of a 32-year-old woman, incidentally discovered to have a mediastinal nodule in the middle compartment on chest computed tomography (CT). The lesion was excised via video-assisted thoracoscopic surgery. Histological evaluation revealed a biphasic cellular architecture comprising epithelioid and spindle cells. Immunohistochemical analysis demonstrated significant positivity for CK5/6 and P40 in epithelial cells, and vimentin and epithelial membrane antigen in spindle cells, with a low proliferation index marked by Ki-67. Noteworthy, fluorescence in situ hybridization (FISH) analysis identified a gene fusion, with a predominant pattern suggestive of fusion gene presence, thus corroborating the diagnosis of MT.
This report underscores the critical role of a multifaceted diagnostic approach, including histopathological, immunohistochemical, and genetic analyses, in the identification of MT. The detection of the gene fusion through FISH analysis provides a robust diagnostic marker, highlighting the necessity for clinical and pathological vigilance for this rare tumor.
化生性胸腺瘤（MT）是原发性胸腺上皮肿瘤中极为罕见的一种变体，其特点是进展缓慢且具有独特的组织病理学特征。它呈现出一种双相模式，其特征为实性上皮和梭形细胞成分，这可能导致与A型胸腺瘤或AB型胸腺瘤的A型成分在诊断上产生混淆。准确诊断对于制定最佳治疗策略和预后评估至关重要。
我们记录了一例特殊病例，一名32岁女性，在胸部计算机断层扫描（CT）时偶然发现中纵隔有一个结节。通过电视辅助胸腔镜手术切除了该病变。组织学评估显示其具有由上皮样细胞和梭形细胞组成的双相细胞结构。免疫组织化学分析显示上皮细胞中CK5/6和P40呈显著阳性，梭形细胞中波形蛋白和上皮膜抗原呈阳性，Ki-67标记的增殖指数较低。值得注意的是，荧光原位杂交（FISH）分析鉴定出一种基因融合，其主要模式提示融合基因的存在，从而证实了MT的诊断。
本报告强调了包括组织病理学、免疫组织化学和基因分析在内的多方面诊断方法在MT识别中的关键作用。通过FISH分析检测到基因融合提供了一个有力的诊断标志物，突出了对这种罕见肿瘤进行临床和病理监测的必要性。
