Atypical Incidental Presentation of Thymolipoma With Macroscopic Appearance Suggestive of Malignancy in Patient Undergoing Coronary Artery Bypass Grafting

Abstract

Purpose: We report the incidental finding of a thymolipoma in a 61-year-old male undergoing urgent CABG with intra-operative findings suggestive of malignant progression. Methods: A 61-year-old male undergoing urgent CABG for triple vessel disease was noted to have a large anterior mediastinal mass upon primary median sternotomy. The 5 cm mass appeared to be infiltrating the SVC, left innominate vein junction and pericardium, with the appearance highly suggestive of malignancy. Given this, and to ensure full oncological clearance, the mass and infiltrated pericardium was excised along with the wall of the SVC and innominate vein which was subsequently repaired using a bovine pericardial patch. Following this, CPB was introduced via 2-stage cannulation and routine coronary artery bypass grafting was performed using LIMA and vein grafts. Results: The patient required a prolonged period of postoperative ventilatory support before being extubated day 4 and went on to have an uneventful recovery. Anatomical histopathology demonstrated the mass was a benign thymolipoma with significant infarction with necrosis and florid histiocytic reaction accounting for the malignant macroscopic appearance. No further follow-up was required. Conclusions: Histiocytic reaction in an infarcting anterior mediastinal thymolipoma can present with macroscopic changes highly suggestive of a malignant process in an otherwise benign lesion.