Teaching Case

A 73-year-old woman, non-smoker, with a history of congestive heart failure and several risk factors for cardiovascular disease, presented with a twenty-day history of left chest pain and dyspnea. The physical examination shows diminished left lung sounds in chest auscultation. Pleuracentese of effusion revealed an exudate, where tumor markers and cultures were negative.

Chest X-ray revealed moderate free pleural effusion on the left (Fig. 1).

Unenhanced thoracic computed tomography (CT) imaging (Fig. 2) showed moderate left pleural effusion and a 5 cm homogeneous soft-tissue oval mediastinal mass in the aortopulmonary window, smoothly marginated and without calcifications or areas of fat attenuation. CT after intravenous administration of iodinated contrast (Fig. 2) revealed marked peripheral enhancement of the mediastinal mass in the arterial phase. The interface of the lesion and adjacent mediastinal structures, namely pulmonary artery trunk, was clear.

Hemangiomas are uncommon benign vascular mediastinal lesions (0.5% of mediastinal masses) [1].

The cause of hemangiomas is unclear but can represent either true neoplasm or developmental vascular anomalies [2]. The anterior mediastinal compartment is most commonly involved, but hemangiomas can be located in any compartment of the mediastinum or involve multiple compartments [1,2,3]. This disease has a higher incidence in young adults, with 75% of cases being under 35 years old [1,4].

At histological examination, the lesions are a combination of large interconnecting vascular spaces lined by vascular endothelium, with interposed stromal elements (such as fat, myxoid and fibrous tissues) and focal organized thrombus, which can calcify as phleboliths [1,2,3]. Hemangiomas can be classified based on the size of vascular spaces as capillary, cavernous or venous, the cavernous ones being more common in the mediastinum [1,2]. Up to half of patients are asymptomatic at diagnosis. The symptoms appear due to compression of adjacent mediastinal structures, with a nonspecific clinical presentation, which includes cough, chest pain and dyspnea[2].

In non-enhanced CT scans, the hemangioma is often a heterogeneous and well-defined soft tissue attenuated mass [1,2]. Infiltration of mediastinal structures is uncommon [2]. The presence of calcifications, normally round and ringlike, is a feature that helps in the diagnosis of hemangioma, however they may be present in other mediastinal lesions, such as teratomas or cartilaginous tumors [1,2]. Intralesional fat attenuation is rare but may be present [2]. On single arterial phase CT scan after contrast administration, the enhancement pattern is uncharacteristic: peripheral, central, mixed or homogeneous patterns have been described [2,3]. On delayed images, progressive and centripetal fill-in enhancement or enhancement «fast in and slow out» are characteristic of hemangiomas, but not always present [1,2,6].

In the magnetic resonance (MR) imaging, hemangiomas are usually presented as heterogeneous lesions on T1 weighted imaging (WI), with isointense and hyperintense nodular areas, the latter attributable to macroscopic fat. Hemangiomas are typically hyperintense on T2 WI fat suppression imaging, similar to the presentation of these lesions in other organs, like the liver, due to the high fluid content [1,6].

The association between pleural effusion and mediastinal hemangioma is poorly understood, with few cases described in the literature.

Imagiological diagnosis of mediastinal hemangioma is difficult and the biopsy of hypervascular lesions carries the risk of uncontrolled hemorrhage [1,4,5]. Hemangioma is a benign tumor, its resection with tharoscopy or open thoracotomy has good results, with rare recurrence. Further than that, preoperative interventional embolization may be performed to reduce the risk of intraoperative bleeding or, as a conservative option, if the lesion is asymptomatic, and careful follow-up is an option [3,4].