A 40-year-old, morbidly obese female presented with severe dyspnea that had progressed over a period of 3 days. She also complained of productive cough, but had no fever or chest pain. Her medical history included bronchial asthma, obstructive sleep apnea, and tobacco abuse. In addition, 5 years before this admission, a computed tomographic (CT) scan performed after an abnormal chest radiograph revealed anterior mediastinal lipomatosis. Because she was asymptomatic at that time, the caring physician elected not to pursue further treatment. Physical examination revealed morbid obesity, facial hirsutism, diffuse expiratory wheezing, altered mental status, and pitting lower extremity edema. Initial vital signs included a blood pressure of 131/77, heart rate of 102, and temperature of 36.2° C. Her baseline oxygen saturation was 91%, but this quickly deteriorated to 61% upon admission. Abnormal laboratory findings included arterial blood gas with pH of 7.28, pCO2 of 124, and pO2 of 69, along with leukocytosis of 11,300 mg/dL. Because of impending respiratory collapse, she was emergently intubated. Chest radiography revealed a widened mediastinal silhouette and extensive bilateral lower interstitial infiltrates (Fig. 1).
A CT scan revealed a huge mass that occupied the entire anterior mediastinum with posterior and caudal displacement of both lungs (Fig. 2). No invasion of great vessels or other structures was noted. The mass consisted of fatty tissue elements interspersed with soft tissue; no calcifications were observed.
Because of the respiratory compromise and the benign radiographic appearance of the tumor, a preoperative biopsy was not obtained. She was taken urgently to the operating room, and a median sternotomy was performed. A large lipomatous mass was found occupying the entire anterior mediastinum draped over the pericardium, extending to both pleural spaces. There was no invasion of contiguous structures by the tumor, and it was easily dissected off of the surrounding organs. Histologic examination of the resected specimen revealed thymolipoma without evidence of malignant degeneration (Fig. 3). Her postoperative course was complicated with pneumonia, which resolved with antibiotic treatment. At the time of discharge, she was breathing easily with stable room air oxygen saturations. However, she continues to have problems with asthma and obstructive sleep apnea.
