A 22-year-old Caucasian man with no complaints or co-morbid conditions presented to our hospital after an abnormal medical check-up before being hired for a job. A chest X-ray revealed an obliteration of the right cardiophrenic sinus by a bosselated mass widening the cardiac shadow (Figure ). The young man was healthy and had good functional capacity. He denied fever, weight loss, previous disease, or any neoplasm history in his family. There was no previous chest X-ray. His physical examination revealed that he was apyrexial, normotensive, and eupneic. His thyroid, lymph node, chest, abdominal, and testis examinations were normal. A 12-lead electrocardiogram demonstrated sinus bradycardia. His chest X-ray showed a mass in the right cardiophrenic sinus with homogeneous, hazy density and a partially well-delineated margin continuous to cardiac shadow. A multi-detector computed tomographic scan showed a septate cystic mass containing septal calcification measuring 8.1cm×6.4cm, which was continuous to the pericardium and caused extrinsic compression of the right atrium. The mediastinal structures did not show any abnormal lymph nodes or features of compression or infiltration (Figure ). By this time, the suspected diagnosis was a pericardial cyst or fat pad. Magnetic resonance imaging suggested a cyst of the pericardium, but with heterogeneous cyst content. Transthoracic two-dimensional and real-time, live three-dimensional echocardiography revealed a normal-sized heart with normal function and blood flow velocities. A rounded extracardiac mass projecting to the right atrium was detected in the parasternal transverse view and apical four-chamber view. For further assessment of the suspicious mass, contrast-enhanced echocardiography was performed, which showed the clear definition of a rounded structure with low opacification with contrast (Figure ). Because of the mass feature, a benign tumor, probably a bronchiogenic cyst, was suspected.
Figure 2 Contrast echocardiographic and computed tomographic images. (A) Contrast-enhanced echocardiographic image obtained after intravenous injection of lipid-encapsulated microbubbles. The apical four-chamber view demonstrates normal left ventricular opacification (more ...)
Surgical excision was accomplished via a median sternotomy. This surgical access was chosen because of clinical suspicion that superior vena cava invasion would necessitate extracorporeal circulation. The tumoral mass was continuous to the right parietal pleura and pericardium. There was no cardiac, pulmonary, or vascular invasion. The surgical approach was successful.
Gross examination showed a rounded tumor measuring 8.0cm × 8.0cm × 4.0cm and weighing 66g. The tumor was predominantly cystic, with a thin, sharply delineated wall filled with sebaceous material and hair. Microscopically, the cyst wall was lined by stratified squamous epithelium with underlying sebaceous glands and hair follicles or by simple ciliated columnar epithelium. Cartilage, adipose tissue, and smooth muscle were also seen in the cyst wall (Figures and ). A histological diagnosis of a mature cystic teratoma was made once immature epithelial, mesenchymal, or neural elements were not found and there was no morphological evidence of malignancy in the tumor. Atrophic thymus was found in the tissue that surrounded the tumor (Figure ). The patient had a good post-operative recovery and was discharged to home on the sixth post-operative day.
Figure 3 Histological sections of mature cystic teratoma (hematoxylin and eosin stain). (A) Skin (SK), mucous (M), and sebaceous glands (S) and smooth muscle (SM) (lens objective, ×5). (B) Ciliated columnar epithelium (CCE), cartilage (Car), mucous glands (more ...)