An unusual case of superior vena cava syndrome caused by the intravascular invasion of an invasive thymoma

Abstract

Superior vena cava syndrome (SVCS) is usually caused by extrinsic compression or invasion of the superior vena cava (SVC) by malignant tumors involving mediastinal structures. Although thymomas are well-known causes of SVCS, cases of SVCS caused by malignant thymomas protruding into adjacent vessels draining the SVC with thrombosis have been very rarely reported worldwide. We experienced a 39-year-old female patient with SVCS that developed after the direct invasion of the left brachiocephalic vein (LBCV) and SVC by an anterior mediastinal mass with a high maximum standardized uptake value on the chest computed tomography (CT) and positron emission tomography-CT. Based on these results, she underwent en bloc resection of the tumor, including removal of the involved vessels, and was eventually diagnosed as having a type B2 thymoma permeating into the LBCV and SVC. We present this case as a very rare form of SVCS caused by an invasive thymoma.

Keywords: Positron-Emission Tomography; Superior Vena Cava Syndrome; Thymoma.

Figure 1

A massive thrombosis in the left brachiocephalic vein and the superior vena cava extending into the right atrium is observed in the chest computed tomography.

Figure 2

The positron emission tomography-computed tomography shows hypermetabolic activity with a maximum standardized uptake value of 6.0 for the anterior mediastinal mass and thrombosis.

Figure 3

(A) The superior vena cava thrombus. Macroscopically, the thrombus is soft and dark red, similar to fish flesh. (B) Microscopically, the tumor cells grow in a solid pattern within the large vessels (H&E stain, ×40). (C) The tumor shows a type B2 thymoma with a predominance of large and polygonal epithelial cells with round or elongated nuclei. Considerable numbers of non-neoplastic small lymphocytes mixed with the tumor can be observed (H&E stain, ×400).