A 43-year-old male presented with chest pain, dyspnoea, and bleeding from the chest wall after biopsy from the chest wall mass. (Panel A) CT examination of chest revealed a large anterior mediastinal mass with erosion of sternum and anterior chest wall. Large foci of calcification, fat, densities resembling teeth were noted in the mass. (Panels B and D, open arrows) Contrast CT demonstrated multiple pseudo-aneurysms arising from right side and anterior wall of the ascending aorta. (Panels C and

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... D, white arrows) Patient underwent emergency excision of mass with the closure of rent in the ascending aorta. During surgery tense mass was noted containing hair and calcific elements. The mass was firmly attached at the site of pseudo-aneurysm which was released, removed with reconstruction of defect in the aortic arch. On histopathology lesion consisted of stratified squamous epithelium, cutaneous appendages, fat, muscles, bone, teeth (Panel F, circled), cartilage, and respiratory epithelium confirming diagnosis of mature cystic teratoma. Though mediastinal teratoma constitutes the common cause of the mediastinal mass, compression of the aorta with formation of pseudoaneurysm is unreported. Pressure effect on the superior vena cava, airways, pulmonary artery, thoracic cage, and myocardium are known. Review of literature revealed a single case of large mediastinal teratoma in relation to the aortic adventitia without aortic aneurysm. State of the art CT provides excellent multiplanar structural details, angiograpic views and surface rendered 3D projections with option of interactive manipulation. Thus availability of such technique at the emergency services makes it one stop shop for the evaluation of complex mediastinal masses. Published on behalf of the