Villalba Julian A, Haramati Adina, Garlin Michelle, Reyes Fabiola, Wright Cameron D, Louissaint Abner, Ackman Jeanne B
James Homer Wright Pathology Laboratories, Department of Pathology, Massachusetts General Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA.
Division of Anatomic Pathology, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA.
Mediastinum. 2023 Mar 20;7:13. doi: 10.21037/med-22-42. eCollection 2023.
The propensity of thymic cysts to mimic solid thymic epithelial tumors (TETs) on computed tomography (CT), on account of attenuation values greater than water and thickened or calcified walls, can lead to non-therapeutic thymectomy. These lesions can fluctuate in volume, CT attenuation, and magnetic resonance imaging (MRI) signal over time. We hypothesized that spontaneous hemorrhage and resorption may contribute to their variable appearance over time.
Completely excised thymic cysts were identified retrospectively over a 20-year period by their pathologic diagnosis. Cysts were excluded if they did not have available presurgical imaging, were not prevascular, were located within or contained an enhancing mass by imaging, or were of non-thymic origin upon microscopic review. Histopathological analysis of all available resected thymic cyst material and radiologic analysis of the cysts on pre-operative imaging were performed.
Upon application of exclusion criteria, we identified 18 thymic cysts from the initial 85 mediastinal cystic specimens. Most cysts were unilocular (11/15, 73%), showed turbid-to-semisolid, hemorrhagic fluid (10/12, 83%) and showed histopathological findings suggestive of intralesional microbleeding (14/18, 78%), remodeling (8/18, 44%), pathological wound healing/scarring of the capsule (16/18, 89%), and fat necrosis in the surrounding thymic tissue (12/18, 67%). On CT, 6/17 (35%) cysts demonstrated wall calcification. Sixty-five percent (11/17) had attenuation values ≥20 Hounsfield units (HU). Two of the 4 cysts imaged by MRI were T1-isointense, one was mixed hyper- and isointense, and one T1-hypointense to muscle, with iso- and hyperintensity indicating hemorrhagic or proteinaceous content. Twenty-five percent (1/4) of cyst walls imaged by MRI were T1/T2-hypointense, indicating presence of calcification, hemosiderin, and/or fibrosis.
Resected thymic cysts in this cohort often showed features suggestive of intralesional microbleeding, inflammation, and fibrosis, which may explain their appearance and behavior over time on CT and MRI.
胸腺囊肿在计算机断层扫描（CT）上倾向于模仿实性胸腺上皮肿瘤（TET），由于其衰减值大于水以及壁增厚或钙化，可能导致非治疗性胸腺切除术。这些病变的体积、CT衰减值和磁共振成像（MRI）信号会随时间波动。我们推测自发性出血和吸收可能导致其随时间出现可变的表现。
通过病理诊断回顾性鉴定20年间完全切除的胸腺囊肿。如果囊肿没有术前可用的影像学资料、不在血管前、影像学显示位于或包含强化肿块，或显微镜检查显示非胸腺来源，则将其排除。对所有可用的切除胸腺囊肿材料进行组织病理学分析，并对术前影像学上的囊肿进行放射学分析。
应用排除标准后，我们从最初的85个纵隔囊性标本中鉴定出18个胸腺囊肿。大多数囊肿为单房性（11/15，73%），显示浑浊至半固体、血性液体（10/12，83%），并且组织病理学结果提示病灶内微出血（14/18，78%）、重塑（8/18，44%）、包膜的病理性伤口愈合/瘢痕形成（16/18，89%）以及周围胸腺组织的脂肪坏死（12/18，67%）。在CT上，6/17（35%）的囊肿显示壁钙化。65%（11/17）的囊肿衰减值≥20亨氏单位（HU）。4个进行MRI成像的囊肿中，2个T1等信号，1个为高信号和等信号混合，1个相对于肌肉为T1低信号，等信号和高信号表明存在出血或蛋白质成分。4个进行MRI成像的囊肿壁中，25%（1/4）为T1/T2低信号，表明存在钙化、含铁血黄素和/或纤维化。
该队列中切除的胸腺囊肿常显示病灶内微出血、炎症和纤维化的特征，这可能解释了它们在CT和MRI上随时间的表现和行为。
