Takeda Tetsu, Eguchi Takashi, Koike Sachie, Koyama Tsutomu, Matsuoka Shunichiro, Miura Kentaro, Hamanaka Kazutoshi, Satoh Yayoi, Uehara Takeshi, Shimizu Kimihiro
Division of General Thoracic Surgery, Department of Surgery, Shinshu University School of Medicine, Matsumoto, Japan.
Department of Diagnostic Pathology, Shinshu University School of Medicine, Matsumoto, Japan.
Mediastinum. 2020 Sep 30;4:28. doi: 10.21037/med-20-46. eCollection 2020.
An association between thymic cyst and thymic epithelial malignancy has been previously reported. However, several case studies have reported granulomas in the thymus with high metabolic activity, mimicking thymic malignancy. Additionally, an inflammatory response provoked by the rupture of cyst walls has been proposed as a pathogenesis of cholesterol granuloma in the thymus. However, the natural growth history of thymic granuloma remains unclear. We herein report the first case demonstrating the natural growth history of a thymic granuloma adjacent to a thymic cyst. Ten-year follow-up of the thymic cyst revealed a growing nodular lesion with high metabolic activity adjacent to the cyst. 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) showed a maximum standardized uptake value of 12.1 in a 2.5-cm solid mass. We performed total thymectomy given a high suspicion of a malignant thymic epithelial tumor. Histopathologic examination revealed a cholesterol granuloma in the thymus, which was directly connected to the thickened region of the cystic wall through a rupture of the wall. This case highlights the importance of considering thymic granuloma as a differential diagnosis for a growing anterior mediastinal nodule with high metabolic activity. Further, the clinical course and histopathologic findings of this case provide supporting evidence for the proposed pathogenesis of thymic granuloma.
此前已有胸腺囊肿与胸腺上皮恶性肿瘤之间关联的报道。然而，多项病例研究报告了胸腺内具有高代谢活性的肉芽肿，类似胸腺恶性肿瘤。此外，有人提出囊肿壁破裂引发的炎症反应是胸腺胆固醇肉芽肿的发病机制。然而，胸腺肉芽肿的自然生长史仍不清楚。我们在此报告首例展示与胸腺囊肿相邻的胸腺肉芽肿自然生长史的病例。对胸腺囊肿进行的十年随访显示，囊肿附近出现一个具有高代谢活性的不断增大的结节性病变。18F-氟脱氧葡萄糖正电子发射断层扫描（FDG-PET）显示一个2.5厘米实性肿块的最大标准化摄取值为12.1。鉴于高度怀疑为恶性胸腺上皮肿瘤，我们实施了全胸腺切除术。组织病理学检查显示胸腺内有一个胆固醇肉芽肿，它通过囊肿壁的破裂与增厚的囊壁区域直接相连。该病例凸显了将胸腺肉芽肿作为具有高代谢活性的前纵隔不断增大结节的鉴别诊断的重要性。此外，该病例的临床病程和组织病理学发现为所提出的胸腺肉芽肿发病机制提供了支持证据。
