Ann Thorac Surg 2005;80:e10-e12
© 2005 The Society of Thoracic Surgeons
Case report
Giant Fibrolipoma in the Mediastinum: An Unusual Case
Jui-Sheng Hsu, MD, PhD
a
,
Wan-Yi Kang, MD
c
,
Gin-Chung Liu, MD
a
,
Eing-Long Kao, MD
b
,
Ming-Tsung Chuang, MD
a
,
Shah-Hwa Chou, MD
b
,
*
a Department of Medical Imaging, Taiwan, Republic of China
b Division of Thoracic Surgery, Department of Surgery, Taiwan, Republic of China
c Department of Pathology, Chung-Ho Memorial Hospital, Kaohsiung Medical University, Taiwan, Republic of China
Accepted for publication May 16, 2005.
* Address reprint requests to Dr Chou, Division of Thoracic Surgery, Department of Surgery, Chung-Ho Memorial Hospital, Kaohsiung Medical University, No. 100 Tz-You 1st Rd, Kaohsiung, 807 Taiwan, Republic of China (Email: u8501122{at}gmail.com).
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Abstract
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A 50-year-old man presented with a middle and posterior mediastinal mass on chest radiograph and computed tomography. Surgical exploration revealed a large dumbbell-shaped lipomatous lesion. Histologic examination confirmed this to be a fibrolipoma. This is the first reported case of fibrolipoma in the mediastinum but outside of the esophagus.
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Introduction
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Lipomas are uncommon mediastinal neoplasms that may affect any body cavity, but are most often located in the anterior mediastinum [1]. In a review of more than 1,000 benign tumors of adipose tissue [2], over 80% were ordinary lipoma, and nearly all of the remainder were angiolipoma, intramuscular lipomas, or lipoblastomas; other types amounted to fewer than 2% of all lipomatous neoplasm. Fibrolipoma is a pathologic variance originating from mesodermal tissue and is composed of fibrous and lipomatous elements. In the large series of esophageal tumors, this tumor rarely appears (3 of 188 cases in 27 years at the Mayo Clinic) [3]. They usually present as pedunculated and intraluminal polyps [4–5], but we believe that the mediastinal fibrolipoma outside of the esophagus has not yet been reported in the English literature. We herein report a case of giant fibrolipoma of the mediastinum outside of the esophagus.
A 50-year-old man without a remarkable medical history presented with a well-delineated abnormal shadow on a routine chest roentgenogram. A computed tomographic scan (Fig 1) demonstrated a well-circumscribed mass with fat (mean density, –74 Hounsfield units [HU]) and soft tissue attenuation (24 HU) in the middle and posterior mediastinum. The esophagus was displaced right posteriorly and the heart was displaced anteriorly.
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Fig 1. Axial (A–B), coronal (C) and sagittal (D) computed tomographic scans showed a well-circumscribed mass with fat and soft tissue attenuation in the middle and posterior mediastinum. (A) The esophagus (arrow) was displaced right posteriorly.
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The tumor was resected for pathologic diagnosis. Access to the mass was accomplished through a left posterolateral thoracotomy. A discrete fibrous fatty mass, which was located within the middle and posterior mediastinum, was removed completely (Fig 2A). The lesion was surrounded by a capsule that was easily separated from the esophagus, trachea, and bronchus. It was resected with a sharp and blunt dissection.
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Fig 2. (A) Intraoperative photograph and (B) surgical specimen showed a dumbbell-shaped giant tumor located within the middle and posterior mediastinum.
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The resected specimen consisted of a 14 cm x 11 cm x 5.5 cm dumbbell-shaped rubbery mass with a thin capsule-like membrane (Fig 2B). On the transverse section, most of the tumor consisted of lobules of yellowish adipose tissue separated by white fibrous septa. No hemorrhage, necrosis, or calcification was noted. Microscopic examination of sections stained by hematoxylin and eosin showed lobules of mature adipose tissue mixed with prominent fibrous septa (Fig 3). The fibrous elements were composed of spindle fibroblasts with focal hyalinization. The adipose elements consisted of mature adipocytes, which were indistinguishable from normal adipose tissue. The histopathologic features were consistent with a fibrolipoma.
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Fig 3. Photomicrograph revealed fatty tissue with prominent fibrous connective tissue and focal hyalinization. (Hematoxylin-eosin, x100, original magnification.)
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Comment
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Lipomas are uncommon mediastinal neoplasms that may be present in any body cavity, but are most often located in the anterior mediastinum [3]. They are reported to represent 1.6% to 2.3% of all primary mediastinal tumors [6]. Lipomas may also arise within a variety of mediastinal structures including the esophagus, airway, and heart. They have an insidious onset that typically goes unnoticed until a well-delineated abnormal shadow on a routine chest roentgenogram is identified [6]. Because of slow growth of the lesions, the presenting symptoms are often due to mass effect (including compression of the primary bronchi, esophagus, phrenic nerve, or vagus nerve). Symptoms can include dysphagia, dyspnea, dry cough, jugular distention, and cardiac arrhythmias [6].
Histologically, classic lipomas were composed of encapsulated, mature adipocytes varying slightly in size. Several other histologic variants were noted, including fibrolipoma, angiolipoma, chondroid lipoma, myolipoma, spindle cell and pleomorphic lipoma, and hibernoma [7]. Fibrolipomas are uncommon variants of lipomas with a mixture of fibrous connective tissue. It has been suggested that fibolipomas arise from the maturation of lipoblastomatosis. Further maturation of both adipose and fibrous tissue results in mature strands of collagen separating fat cells into lobules, characteristic of a fibrolipoma [4–5].
Mediastinal lipomas resemble other soft-tissue masses on chest roentgenogram and are commonly categorized by location as localized mediastinal (usually at the cardio-diaphragmatic angle), cervico-mediastinal (extending into the neck), or transmural (penetrating the chest wall, usually in the upper anterior mediastinum). On computed tomography, lipomas have homogeneous fat attenuation of approximately –100 HU. Magnetic resonance imaging can also show the extent and fatty nature of the lesion. Simple excision of this well-demarcated tumor can be performed if it is symptomatic.
Lipomatous tumors are common and account for approximately half of all soft-tissue tumors in surgical series. The computed tomographic and magnetic resonance images of patients with fatty masses are usually sufficiently characteristic to suggest their lipomatous nature, and often allow a specific diagnosis. However, the distinction among lipoma, lipoma variants, and liposarcomas are frequently a diagnostic dilemma.
Lipoma is a benign mesenchymal tumor in which the lesion closely resembles normal fat. The resemblance is so great that the fat within a lipoma can not be distinguished histologically from normal fat; however, there are biochemical and ultrastructural differences. Lipoma variants and liposarcomas also resemble lipomas, although they tend to be larger and are often traversed by dense bands of collagen, have gelatinous areas, and have adipocytes that show greater variation in size than an ordinary lipoma [6]. Clearly, fibrolipoma is a combination tumor of fibromatous and lipomatous elements. In addition, liposarcomas contain enlarged adipocytes, atypical hyperchromatic cells with angular nuclei and lipoblasts [6].
Surgery is the treatment of choice for intrathoracic lipomatous tumors of any histologic type, and most surgical treatments are curative. However, although fibrolipomas are histologically benign, they are often believed to be clinically malignant because of frequent recurrence during an extended period of time [8]. Jesberg [8] described a case of fibrolipoma of the pyriform sinus that had three major recurrences at 10 to 15-year intervals during a 36-year period. A careful follow-up for any other new lesions is required.
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References
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Abstract
Introduction
