Malignant thymic epithelial tumors: CT-pathologic correlation

OBJECTIVE. The purpose of our study was to describe and compare the CT and pathologic findings of atypical thymoma and thymic carcinoma. MATERIALS AND METHODS. Twenty-seven consecutive patients (14 men, 13 women ranging in age from 22 to 77 years [mean age, 52 years]) with pathologicall y proven atypical thymoma (n = 9) and thymic carcinoma (n = 18) constituted the study population. The chest CT findings in each of the 27 patients wer e reviewed retrospectively in consensus by two chest radiologists. These fi ndings were correlated with pathologic findings. RESULTS. The tumors were located in the anterior mediastinum. and most tumo rs had a lobulated margin (24/27, 89%). Atypical thymomas were significantl y smaller (mean, 4.7 cm) than thymic carcinomas (mean, 7.2 cm) (p = 0.041) on CT. The findings of invasion of the great vessels, lymph node enlargemen t, extrathymic metastases, and phrenic nerve palsy were seen only in patien ts with thymic carcinoma. The frequencies of necrosis, intratumoral calcifi cation. pleural effusion, pleural implants, pericardial effusion, and oblit eration of the mediastinal fat plane were not significantly different betwe en atypical thymomas and thymic carcinomas (p > 0.05). Various histologic s ubtypes were included in thymic carcinoma. The tumor necrosis and calcifica tion seen on CT were confirmed at pathologic examination. CONCLUSION. When a large thymic tumor appears with invasion of the great ve ssels, lymph node enlargement, phrenic nerve palsy, or extrathymic metastas es on CT, thymic carcinoma rather than atypical thymoma should be considere d.