We report a case of a 44-year old female who presented to her physician complaining of mild dyspnea. A follow-up chest X-ray and chest computed tomography scan revealed a giant bilateral intrathoracic mass, filling the right thoracic cavity and extending across the anterior mediastinum into the left chest cavity. This large mass caused a marked shift in the midline structures, displacing the heart to the left hemi-thorax. The patient underwent surgical removal of the thoracic and breast mass, with histologic examination confirming the diagnosis of a giant intrathoracic lipoma, weighing 4,320 grams and measured 34 × 28 × 11 cm. It is the largest intrathoracic lipoma documented in the modern literature. Case presentationA 44-year old African American female who worked as a phlebotomist presented to her primary care physician complaining of mild shortness of breath and a 4-pillow orthopnea for many years (>10 years). She was a nonsmoker, and maintained a healthy weight of 142 pounds for her 68" height. Her past medical history was significant only for uterine fibroids, for which she had undergone a myomectomy. She had conceived six healthy children, and the remainder of her family had no health problems. A subsequent chest x-ray and CT scan revealed a large mediastinal mass which occupied the majority of the right thoracic cavity and further extended across the anterior mediastinum into the left thoracic cavity ( figure 1A). The posteroinferior portion of the mass revealed several areas of dystrophic ring-type calcifications within a field of scattered dense soft tissue elements. These were thought to possibly represent a pleural-based liposarcoma, lipoma, teratoma, teratocarcinoma, or invasive thymoma of the anterior mediastinum. The mass shifted the heart and mediastinal vascular structures to the left of midline.In order to remove this large intrathoracic mass, the patient was explored through a transverse sternothoracotomy (clam-shell incision) to allow complete access to both pleural spaces and the mediastinum. Upon exposure of the anterior mediastinum, a large mass was visualized crossing this area and extending into both thoracic cavities ( figure 1B). The mass further extended into the left thoracic cavity and displaced the lower lobe of the left lung. The gross appearance was that of a thinly encapsu-