The value of enhanced computed tomography combined with magnetic resonance imaging in the differential diagnosis of thymomas and thymic cysts before operation

BACKGROUND: We evaluated the application of enhanced computed tomography (CT) combined with magnetic resonance imaging (MRI) to preoperative diagnosis of thymomas and thymic cysts. METHODS: The patients admitted to General Hospital of Tianjin Medical University with anterior mediastinal masses (maximum diameter <5 cm) from 2016 to 2020 were analyzed. In total, 81 patients had been included, including 43 (13 male, 30 female) thymomas (28 cases of myasthenia gravis) and 38 (17 male, 21 female) thymic cysts (2 cases of myasthenia gravis). The median age of the patients with thymomas and thymic cysts was 56 (48–65) and 56.5 (50.8–64) years, respectively. The features of thymomas and thymic cysts revealed on enhanced CT, MRI, and clinically were compared, and we evaluated the diagnostic performance of enhanced CT combined with MRI. RESULTS: Most thymomas exhibited iso-signal intensity on T1- and T2-weighted imaging (T2WI) and iso- or high-signal intensity on diffusion-weighted imaging. In masses with diameters <3 cm, diffusion-weighted imaging (DWI) and CT were not statistically significant (P>0.05). In masses with diameters of <5 and <3 cm, the area under the receiver operating characteristic curves (AUC) of the enhanced 120sCT value were 0.94 and 0.95, respectively, and those for apparent diffusion coefficient (ADC) value were 0.92 and 0.91, respectively. In masses with diameters <5 cm, the diagnostic rates of enhanced CT, MRI, and enhanced CT combined with MRI for thymomas were 40.5%, 64.9%, and 70.3%, respectively, and those for thymic cysts were 37.5%, 62.5%, and 71.9%, respectively. In masses with diameters <3 cm, the diagnostic rates of enhanced CT, MRI, and enhanced CT combined with MRI for thymomas were 40.9%, 68.2%, and 77.3%, respectively, and those for thymic cysts were 32.0%, 64.0%, and 68.0%, respectively. CONCLUSIONS: Enhanced CT combined with MRI is superior to enhanced CT or MRI alone for preoperative differential diagnosis of thymomas and thymic cysts with diameters of <5 and <3 cm.