Ann Thorac Surg 2000;70:662-663
© 2000 The Society of Thoracic Surgeons
Case report
Intermittent brachiocephalic vein obstruction secondary to a thymic cyst
Jeffrey S. Miller, MDa,
Scott A. LeMaire, MDa,
Michael J. Reardon, MDa,
Joseph S. Coselli, MDa,
Rafael Espada, MDa
a Division of Cardiothoracic Surgery, Department of Surgery, Baylor College of Medicine, Houston, Texas, USA
Address reprint requests to Dr Miller, Department of Surgery, Baylor College of Medicine, 6565 Fannin, Suite A886, Houston, TX 77030
e-mail: jmiller{at}bcm.tmc.edu
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Abstract
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Mediastinal thymic cysts are usually asymptomatic and found incidentally on a routine chest roentgenogram. Rarely, they may cause symptoms of vascular obstruction. A 55-year-old woman presented with intermittent swelling in her left neck. The swelling was positional and was worse while supine and disappeared while upright. Evaluation revealed a thymic cyst causing extrinsic compression of the left brachiocephalic vein. The cyst was resected with complete resolution of the left neck swelling.
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Introduction
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Vascular obstruction of the superior vena cava or brachiocephalic vein may be caused by large, malignant tumors of the mediastinum. Rarely, a benign cystic lesion in the anterior mediastinum adjacent to the brachiocephalic vein may result in extrinsic compression and vascular obstruction. We recently encountered a patient with positional swelling of her left neck secondary to intermittent compression of the left brachiocephalic vein by a small, benign thymic cyst.
A 55-year-old woman with a history of noninsulin-dependent diabetes mellitus and fibromyalgia presented with a complaint of left neck fullness. She described a mass the size of a grapefruit in her left neck. She stated that during the daytime, the mass was usually much smaller and at times completely resolved. Physical examination in the supine position was remarkable for a 6-cm, nontender, diffuse mass along the anterior border of the left sternocleidomastoid. When the patient sat upright on the examination table, the mass became significantly smaller. A contrast-enhanced computed tomography (CT) scan of the neck demonstrated significant dilatation of the left internal jugular vein (Fig 1). A CT scan of the chest revealed a well-circumscribed, 2.5-cm low density soft tissue mass in the anterior mediastinum on the anterior border of the left brachiocephalic vein (Fig 2). The patient underwent median sternotomy and thymectomy. A 2.5-cm cystic mass was identified within the thymic tissue anterior to the left brachiocephalic vein. Pathology revealed a benign thymic cyst with thymic remnants. The postoperative course was without complication and at the 2-month follow-up the patient reported no further swelling in her left neck.
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Fig 1. Contrast-enhanced computed tomography scan of the neck showing significant dilatation of the left internal jugular vein.
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Fig 2. Computed tomography scan of the chest demonstrating a well-circumscribed, 2.5-cm mass in the prevascular space of the anterior mediastinum. The tumor is anterior to the left brachiocephalic vein.
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Comment
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Thymic cysts are uncommon lesions and account for less than 2% of all mediastinal tumors [1]. They may be either congenital or acquired. Congenital thymic cysts are usually unilocular and represent derivatives of embryonal thymic tissue; acquired cysts are more commonly multilocular and result from involutionary changes in the gland. Histologically, these cysts are composed of a thin capsule lined with cuboidal, squamous, or columnar epithelium. Thymic tissue is present in the wall and the cyst most often contains a clear serous fluid. Over time, the cyst may degenerate and develop a thickened, calcified capsule with lymphocytic infiltration, cholesterol clefts, or fibrous tissue. In addition, the fluid may become thick, bloody, or heterogeneous. Occasionally, the cyst may enlarge rapidly secondary to hemorrhage or infection.
Thymic cysts are usually asymptomatic and discovered incidentally on a chest roentgenogram. Radiographically, these lesions appear as smooth, homogeneous, well-circumscribed tumors in the anterior mediastinum with a density on CT scan approximating that of water [2]. Symptomatic thymic cysts resulting in chest pain, cough, hoarseness, dyspnea, and dysphagia have been reported [3–6]. Other unusual presentations have included Horner’s syndrome [7], tracheomalacia [8], and cardiac tamponade [9].
The diagnosis and treatment of thymic cysts remains controversial. Although thymic cysts are benign lesions, it may be difficult to distinguish them radiographically from potentially malignant lesions with cystic changes, including thymoma, teratoma, lymphoma, or seminoma. Treatment options include careful observation with close follow-up, diagnostic or therapeutic aspiration using CT guidance or mediastinoscopy, and surgical exploration and excision. Most authors agree that surgical resection remains the treatment of choice for definitive diagnosis and cure.
This case of a small, benign thymic cyst causing obstruction of the left brachiocephalic vein with associated left neck swelling was unique, and the intermittent nature of this swelling was unusual. The intermittent swelling may be explained by positional obstruction of the left brachiocephalic vein, as the left neck swelling was significantly worse while the patient was supine and nearly resolved when the patient was upright. As with most thymic cysts, surgical resection in this patient resulted in definitive diagnosis, resolution of symptoms, and cure.
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References
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Accepted for publication December 17, 1999.
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Abstract
Introduction
