Objective: The aim of this study was to investigate the prevalence and characteristics of nodular lesions in the anterior mediastinum that had been found incidentally on screening chest computed tomography (CT) in asymptomatic subjects. Methods: We included 56,358 consecutive participants (mean age 52.4 ± 10.5 years; male‐female ratio 35,306:21,052) who underwent a baseline low‐dose chest CT scan as part of a health checkup from 2006 through 2013. After the presence of anterior mediastinal nodular lesion had been confirmed, their CT findings, confirmatory diagnosis, and interval CT scan were reviewed. The standardized prevalence ratio for thymic epithelial tumor was calculated on the basis of the Republic of Korea cancer statistics for 2014. Results: Of the 56,358 participants, 413 (0.73%) had lesions (95% confidence interval: 0.66–0.80%); the prevalence increased with age (p <0.001) and a history of malignancy (p = 0.005). Of the lesions, 85.2% were smaller than 2 cm, 61.3% were round, and 80.2% had CT attenuation higher than 20 Hounsfield units. Among 51 proven cases, 39 lesions (76.9%) were benign and 12 (23.1%) were malignant. The standardized prevalence ratio for thymic epithelial tumor was 2.04 (95% confidence interval: 1.01–3.42). Of 11 resected thymic epithelial tumors, five were carcinomas, 10 were stage I or II, and all were completely resected without recurrence. Of the 237 unconfirmed cases with a follow‐up CT scan, 82.2% were stable, 8.9% had increased, and the other 8.9% had decreased. Conclusions: The prevalence of incidental nodular lesion was 0.73%. Most lesions had CT features that were indistinguishable from thymic epithelial tumors, but a considerable portion of the lesions were suspected to be benign. Incidental thymic epithelial tumors were more prevalent than clinically detected tumors, were early‐stage cancer, and showed favorable outcomes.

中文翻译：

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无症状患者胸部 CT 上偶发的前纵隔结节性病变

目的：本研究的目的是调查无症状受试者在筛查胸部计算机断层扫描 (CT) 时偶然发现的前纵隔结节病变的患病率和特征。方法：我们纳入了 56,358 名连续参与者（平均年龄 52.4 ± 10.5 岁；男女比例 35,306:21,052），他们在 2006 年至 2013 年期间接受基线低剂量胸部 CT 扫描作为健康检查的一部分。结节病灶已确诊，复查其 CT 表现、确诊和间隔 CT 扫描。胸腺上皮肿瘤的标准化患病率是根据 2014 年韩国癌症统计数据计算的。 结果：在 56,358 名参与者中，413 人（0.73%）有病变（95% 置信区间：0.66-0.80%）；患病率随着年龄（p <0.001）和恶性肿瘤病史（p = 0.005）而增加。在病变中，85.2% 小于 2 cm，61.3% 为圆形，80.2% 的 CT 衰减高于 20 Hounsfield 单位。51例确诊病例中，良性病变39例（76.9%），恶性病变12例（23.1%）。胸腺上皮肿瘤的标准化患病率为 2.04（95% 置信区间：1.01-3.42）。在切除的 11 例胸腺上皮肿瘤中，5 例为癌，10 例为 I 或 II 期，全部切除无复发。237 例后续 CT 扫描未确诊病例中，82.2% 稳定，8.9% 增加，另外 8.9% 减少。结论：偶发性结节病变的发生率为0.73%。大多数病变具有与胸腺上皮肿瘤无法区分的 CT 特征，但相当一部分病变被怀疑是良性的。偶然的胸腺上皮肿瘤比临床检测到的肿瘤更普遍，是早期癌症，并显示出良好的结果。