MRI: An MRI for suspected aortic dissection was obtained. The MRI showed no dissection but demonstrated a 4 cm anterior mediastinal mass with possible connection to the ascending aorta. In light of the clinical presentation, the possibility of a large, anterior mediastinal, false aneurysm could not be excluded.

CT: After the MRI, a contrast CT failed to show an aortic connection to the mass.

Aortogram: An aortogram confirmed the absence of a false aneurysm.

EKG: Normal

Serum troponin: Normal

Ventilation/perfusion scan: Not done. An embolus was thought to be unlikely with normal respirations and EKG.

Radiologic Findings

The contrast CT showed a rounded mass with central low attenuation anterior to the ascending aorta (A) and pulmonary artery trunk (P).

What is the differential diagnosis? Answer

Laboratory examination showed WBC 6.3 k/µl, Hb 13.9 g/dl, Hct 46%, and plts 197 k/µl. Electrolytes were normal. Arterial blood gases showed pH 7.38, pCO2 43 mm Hg, and pO2 132 mm Hg on 3 L of oxygen by nasal cannula. The pain abated with morphine and disappeared after 2 days. The blood pressure stabilized at 145/80. On the fourth hospital day, he underwent a median sternotomy for excision of the chest mass.

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The differential diagnosis includes aortic pseudoaneurysm, thymoma, thymic carcinoma, cyst, lymphoma, mediastinal thyroid (mass is not contiguous with the cervical thyroid gland), and germ cell tumor.

Clinical summary Image 1

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