A 46-year-old male presents to the emergency department with an episode of oppressive, precordial pain radiating to the neck- He is diagnosed with acute myocardial infarction and treated with angioplasty and 3 farmacoactive stents. 24 hours later the patient has fever and thoracic pain that increases with deep inspiration.
A plain X-ray was performed to exclude acute thoracic complications and it showed occupation of the anterosuperior mediastinum with enlargement of the cardiomediastinal silhouette. Patchy opacifications or pleural effusion were absent (figure 1).
Due to the positive findings in the chest x-ray, a thoracic computed tomography (CT) was performed that showed an occupation of the anterior mediastinum by a solid hypodense homogeneous mass with polylobulated shape and ill-defined margins. The mass is in intimate contact with the great vessels and the pericardium. There was no active bleeding point or contrast extravasation (figure 2).
A chest magnetic resonance (MRI) was also performed and it showed a hyperintense mass in FLAIR weighted-image, but it remains with high intensity in fat suppression sequences. This helps to differentiate it from other lesions that might have a fatty component such as thymoma or germ cell carcinomas. The mass presents areas with restriction to water diffusion (C and D) which indicates the different stages of the hematoma. Highly cellular tumours such as lymphoma would show homogeneous restriction to water diffusion (figure 3).
A chest CT performed one year later revealed an almost complete resolution of the lesion, confirming the diagnosis of mediastinal hematoma (figure 4).
The anterior mediastinum might be occupied by different lesions because it is composed of the thymus, lymph nodes, adipose tissue, nerves, vessels, and thoracic thyroid. However, complications of surgery/ treatment therapy can mimic a mediastinal mass such as mediastinal hematoma, aortic dissection, aneurysm rupture or arteriovenous fistula [1,2].
Mediastinal hematoma is a complication secondary to thoracic trauma or surgery complications, and, rarely, it can occur spontaneously in patients taking anticoagulants [3,4, 5].
However, coughing and vomiting, among others, are predisposing factors to develop spontaneous mediastinal hematoma [3,5].
The consequence of the mediastinal hematoma is the compression of other structures such as the airway, a life-threatening situation [4,5, 6].
It might be difficult to recognize it on x-ray, which delays its diagnosis, so it is crucial to have a compatible clinical history 
Patients normally present with chest pain and dyspnea. Other symptoms less common are respiratory distress, tachycardia, dysphagia, dysphonia or neck wall ecchymosis [4,5]. EKC alterations might be seen . A chest x-ray is primarly performed to exclude complications such as pneumothorax or bronchoaspiration, but if a vascular complication is suspected, then an angiography or angioCT should be performed.
The first imaging technique usually performed is a chest radiography, and in cases of large hematomas or aneurysms, it shows an anterior mediastinal enlargement with obscuration of the aortic arch and displacement of mediastinal structures.
However, the IV contrast-enhanced CT through the chest is more precise and can detect a soft-tissue mass with areas of different attenuation that indicates haemorrhage and allows to measure the size of the hematoma, the extension, detection of active bleeding or other complications. [1,3,.
The angiography is an imaging technique used with diagnostic and therapeutic purposes that localizes the exact point of bleeding and in cases where the conservative treatment is ineffective or in hemodynamically unstable patients, it provides embolization of the bleeding vessel [5,6,7]
Finally, to consider the diagnosis of mediastinal hematoma, it is highly important to correlate the imaging findings (mediastinal widening in a patient with a previous normal x-ray) with the clinical history, normally patient with chest pain and previous surgery.
CT is performed to evaluate the extension of the hematoma and the presence of active bleeding or compression of other structures. In some cases, an angiography is performed to diagnose and treat active bleeding .
Patients should have a follow-up chest radiograph to assess for the resolution of the hematoma.
Treatment options are conservative therapy in cases of asymptomatic patients or absence of active bleeding or endovascular surgery in cases of life-threatening situations or ineffectiveness of conservative therapy. In these cases, transcatheter embolization is the preferred treatment option [4,5,6,7].
Written informed patient consent for publication has been obtained.
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