An Extremely Uncommon Case of an Internal Thoracic Vein Aneurysm

Venous aneurysms in the anterior mediastinum are rare. While there are scattered reports on thoracic venous aneurysms, such as those involving the azygos or brachiocephalic veins, those involving the internal thoracic vein are exceedingly rare. We herein report the case of an internal thoracic venous aneurysm that was initially suspected of being a tumor and diagnosed intraoperatively.

A 50-year-old woman underwent CT during hospitalization for cerebral infarction, which revealed a well-defined 14-mm nodular lesion in the anterior mediastinum. Contrast-enhanced CT performed 4 months later showed that the anterior mediastinal lesion had increased to 16 mm and exhibited slight contrast enhancement. ¹⁸F-fluorodeoxyglucose PET/CT demonstrated only a slight uptake in the anterior mediastinal lesion with no abnormal uptake elsewhere. Thymic epithelial tumors and cysts were included in the differential diagnosis, and video-assisted thoracoscopic surgery was planned. Intraoperative findings revealed a dark-red nodule beneath the mediastinal pleura. The right internal thoracic vein was observed to flow into the nodule and an outflow vessel draining into the right brachiocephalic vein was identified. Based on these findings, the lesion was diagnosed as an internal thoracic venous aneurysm. The right internal thoracic vein and outflow vessel were ligated, and the nodule was resected. A histopathological examination confirmed the diagnosis of venous aneurysm.

Although extremely rare, venous aneurysms can occur in the internal thoracic vein. This condition should be considered in the differential diagnosis of enhancing solid nodules of the anterior mediastinum.