Investigation on Computed Tomography Features of Primary Thymic Atypical Carcinoid Tumors

The thymic atypical carcinoid tumors (aTCs) are rare. The computed tomography (CT) features of aTC were poorly studied, and researches under this topic with large samples are in a small quantity in the literature. Our aim was to investigate the CT features of aTC.

Eleven cases of aTC (7 men and 4 women; mean age, 56 ± 16 years) proved by pathology were retrospectively analyzed. All the patients underwent contrast-enhanced CT scans with dual phase (25-30 and 60-70 seconds) after contrast agent injection. Two experienced radiologists analyzed the imaging findings. The observing indexes of CT features were based on standard CT reporting terms of mediastinal masses suspicious for thymic malignancy, particularly on the findings of marginal cystic/necrotic component (MCC) sign and hypervascular sign in tumors.

All the tumors were located in the anterior and/or middle mediastinum and heterogeneous parenchyma, with moderate to marked enhancement, and had multiple cystic/necrotic components. The maximum diameter of lesions ranged from 5 to 24 cm. Among the 11 patients involved in this study, 6 patients had distant metastases, all of which were identified as skeletal metastases; 9 cases showed MCC sign only at the margin (3 cases) or at both marginal and central margins (6 cases), and 5 cases showed hypervascular sign.

Our results suggested that the MCC and hypervascular signs should be included as characterization in addition to the standard features for the diagnosis of aTC.