Age‐ and gender‐specific disease distribution and the diagnostic accuracy of CT for resected anterior mediastinal lesions

BACKGROUND: Anterior mediastinal lesions account for approximately half of all mediastinal masses and computed tomography (CT) is known to exhibit limited differentiating performance. Our aim was to evaluate the age‐ and gender‐specific distribution of anterior mediastinal lesions and the diagnostic accuracy of multi‐detector CT (MDCT). METHODS: This retrospective study included 549 consecutive patients with proven anterior mediastinal lesions and diagnostic MDCT scans. The age‐ and gender‐specific distribution of proven diagnoses and diagnostic accuracy were reviewed. The CT features of malignant and benign diseases having the lowest accuracy were compared with those of the most commonly misdiagnosed diseases. RESULTS: The proportion of malignancy showed a V‐shape relationship with age (lowest, 52.7% [50s]). The most prevalent malignancies were lymphoma (20s), lymphoma/thymoma (30s), thymoma (40s–50s), and thymoma/thymic carcinoma (≥60s). The most prevalent benign diseases were thymic remnant/hyperplasia (20s–30s), and thymic bed cyst (≥40s). The first‐choice diagnostic accuracy of MDCT decreased with age regardless of gender: 75.4% (20s), 75.0% (30s), 67.8% (40s), 58.5% (50s), and 53.4% (≥60s), primarily due to incorrect diagnoses of thymic bed cyst and thymic carcinoma (accuracy, 42.3% and 30.5%), which were prevalent in older patients and mostly misdiagnosed as thymoma. The most powerful differentiating MDCT features were water attenuation (≤20 HU) (OR, 42.7 [95%CI, 8.8–‐208.3], P < 0.001) for thymic bed cyst and mediastinal lymphadenopathy (6.8 [1.7–27.2], P = 0.006) for thymic carcinoma, but both showed low sensitivity (34.5% and 18.6%, respectively). CONCLUSIONS: MDCT accuracy depended on age, owing to the age‐specific distribution of thymic carcinoma and thymic bed cyst, which frequently lacks distinguishable CT features from thymoma.