1 clinical data patient, male, 46 years old. He was admitted to the hospital on June 29, 2023 because of "chest tightness with occasional chest pain for more than half a month". Before admission, chest enhanced CT showed a patchy mixed density shadow on the left side of the anterior upper mediastinum (Fig. 1), which was about 6.3 cm × 5.1 cm × 5.8 cm in size and irregular in shape. The enhancement scan showed uneven and continuous enhancement, and small patchy low-density without enhancement shadow was seen inside, which disappeared from the fat space of adjacent large vessels and closely seemed to have invasion with the pericardium. A patchy low enhancement filling defect (about 2.6 cm × 2.1 cm) was seen in the left brachiocephalic vein (Fig. 2). Consider malignant thymoma and left brachiocephalic vein tumor thrombus formation. After admission, we improved the relevant auxiliary examination and diagnosed malignant thymoma, ct3n0m0 stage Ⅲ a (ajcc/uicc 8th Edition). On July 11, 2023, open chest exploration thymectomy was performed: the median sternal incision was taken.