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Korean J Radiol. 2019 Apr;20(4):671-682. doi: 10.3348/kjr.2018.0400.

Distinguishing between Thymic Epithelial Tumors and Benign Cysts via Computed Tomography.

Lee SH1,2, Yoon SH1,3, Nam JG1,2, Kim HJ1,2, Ahn SY4,5, Kim HK1,2, Lee HJ1,2, Lee HH6, Cheon GJ6, Goo JM1,2,7.

Author information

1
Department of Radiology, Seoul National University College of Medicine, Seoul, Korea.
2
Department of Radiology, Seoul National University Hospital, Seoul, Korea.
3
Department of Radiology, Seoul National University Hospital, Seoul, Korea. yshoka@gmail.com.
4
Department of Radiology, Konkuk University School of Medicine, Seoul, Korea.
5
Department of Radiology, Konkuk University Medical Center, Konkuk University School of Medicine, Seoul, Korea.
6
Department of Nuclear Medicine, Seoul National University College of Medicine, Seoul National University Hospital, Seoul, Korea.
7
Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Korea.

Abstract

OBJECTIVE:

To investigate whether computed tomography (CT) and fluorine-18-labeled fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) may be applied to distinguish thymic epithelial tumors (TETs) from benign cysts in the anterior mediastinum.

MATERIALS AND METHODS:

We included 262 consecutive patients with pathologically proven TETs and benign cysts 5 cm or smaller who underwent preoperative CT scans. In addition to conventional morphological and ancillary CT findings, the relationship between the lesion and the adjacent mediastinal pleura was evaluated qualitatively and quantitatively. Mean lesion attenuation was measured on CT images. The maximum standardized uptake value (SUVmax) was obtained with FDG-PET scans in 40 patients. CT predictors for TETs were identified with multivariate logistic regression analysis. For validation, we assessed the diagnostic accuracy and inter-observer agreement between four radiologists in a size-matched set of 24 cysts and 24 TETs using a receiver operating characteristic curve before and after being informed of the study findings.

RESULTS:

The multivariate analysis showed that post-contrast attenuation of 60 Hounsfield unit or higher (odds ratio [OR], 12.734; 95% confidence interval [CI], 2.506-64.705; p = 0.002) and the presence of protrusion from the mediastinal pleura (OR, 9.855; 95% CI, 1.749-55.535; p = 0.009) were the strongest CT predictors for TETs. SUVmax was significantly higher in TETs than in cysts (5.3 ± 2.4 vs. 1.1 ± 0.3; p < 0.001). After being informed of the study findings, the readers' area under the curve improved from 0.872-0.955 to 0.949-0.999 (p = 0.066-0.149). Inter-observer kappa values for protrusion were 0.630-0.941.

CONCLUSION:

Post-contrast CT attenuation, protrusion from the mediastinal pleura, and SUVmax were useful imaging features for distinguishing TETs from cysts in the anterior mediastinum.

KEYWORDS:

Computed tomography; Cystic mass; FDG-PET/CT; Mediastinum; Thymic tumor

Conflict of interest statement

The authors have no potential conflicts of interest to disclose.

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