CT and MRI findings of thymic carcinoid

Objective: To evaluate the CT and MRI findings of thymic carcinoid and to compare these findings with previously published findings of thymoma. Methods: 11 cases of pathologically proven thymic carcinoid were reviewed retrospectively. Three patients had typical carcinoid, and eight patients had atypical carcinoid. The characteristics of the tumours and related thoracic abnormalities were assessed in each case on CT and/or MRI by two chest radiologists. The final decisions on the findings were reached by consensus. Results: Thymic carcinoids were more likely to have a large mass (ranging from 18 to 105 mm), irregular contours (n = 8), heterogeneous intensity on T-2 weighted images (n = 6; eight patients underwent MRI), heterogeneous enhancement (n = 9) and local invasion (n = 7). A necrotic or cystic component was identified in seven patients (one typical carcinoid and six atypical carcinoids). Lymphadenopathy was seen in four patients. Septum, capsule, haemorrhage and calcification were seen in three patients, two patients, two patients and one patient, respectively, with atypical carcinoid. Conclusion: Thymic carcinoids tend to have a high prevalence of large masses, irregular contours, heterogeneous intensity on T-2 weighted images, heterogeneous enhancement and local invasion on CT and/or MRI. A necrotic or cystic component is often seen in atypical carcinoid. Advances in knowledge: Radiologic features of thymic carcinoid mimic those of high-risk thymomas and/or thymic carcinomas.