A case of mediastinal hemangioendothelioma treated with resection of superior vena cava and brachiocephalic vein

Abstract

A 67-year-old woman complaining of bronchial asthma attack was admitted to Seikeikai hospital for further evaluation of mediastinal mass detected incidentally on a screening chest roentgenogram. On chest computed tomography scan, a soft tissue density, unhomogenious, 35-mm spherical mass containing calcifications was located in the superior mediastinum in contact with the superior vena cava (SVC). Enhanced T1-weighted magnetic resonance images (MRI) showed staining in part of the mass and the same part of the mass demonstrated extremely higher intensity on the T2-weighted images, indicating the mass might have been a teratoma or hemangioma.
We first attempted video assisted thoracic surgery (VATS), but the tumor adhered strongly to the SVC and also involved the right phrenic nerve. We thus performed thoracotomoy via the 5th intercostal space, and a frozen section of the mass involving the phrenic nerve was histologically examined intraoperatively. The histological diagnosis was benign hemangiopericytoma. The phrenic nerve was conserved, even though some of the tumor around it remained, but the right brachiocephalic vein and the part of the SVC showing strong adhesion to the tumor were excised to resect it. Histological examination revealed that the tumor was composed of clusters of well formed capillary vessels with focal areas consisting of sheets of epithelioid cells with poorly formed vascular channels. Endothelial cells had large cytoplasmic vacuoles containing intact or fragmented red blood cells.
No necrosis or mitosis was found in the tumor cells. The tumor cells stained strongly positive for factor VIIIassociated antigen and vimentin and negative for epithelial membrane antigen (EMA), Desmin and Cytokeratin (data not shown), leading to the diagnosis of benign hemangioendothelioma. Hemangioendotheliomas are uncommon lesions of the mediastinum and 35 case reports from 1963 are listed in this paper, including our case.