Asian Cardiovasc Thorac Ann 1999;7:62-64
© 1999 Asia Publishing EXchange Pte Ltd
Thymolipoma of Anterior Mediastinum
Shyam Kumar Singh Thingnam, MCh,
Deepak Puri, MS,
Neerod Kumar Jha, MCh,
Rakesh Kumar Vasishta, MD1,,
Rajendar Krishan Suri, MS
Department of Cardiovascular & Thoracic Surgery India
1 Department of Pathology Postgraduate Institute of Medical Education and Research Chandigarh, India
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For reprint information contact: Rajendar Krishan Suri, MS Tel: 91 172 715 977 Fax: 91 172 540 401 House no. 59, Sector 24-A, Chandigarh 160023, India.
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Abstract
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Thymolipoma is a very rare benign anterior mediastinal tumour. Most patients are asymptomatic but a few may present with clinical symptoms attributable to its huge size or less frequently, with myasthenia gravis. We report a case of huge thymolipoma occupying almost two thirds of the thorax in a 25-year-old female, which caused collapse of the lower lobe of the left lung simulating cardiomegaly on a chest skiagram. The tumor was successfully removed en bloc through a median sternotomy combined with an extended left anterolateral thoracotomy. There was no clinical or radiological evidence of residual tumor at the 1-year follow-up.
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Introduction
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Thymolipoma is a very rare benign anterior mediastinal tumor first reported by Lange in 1916.1 Only 50 such cases have been reported in the world literature.2 The majority of the patients are asymptomatic and diagnosed incidentally on routine chest skiagram. Because of the large size and pliability, a thymolipoma can drape around the heart and slump onto the diaphragm adapting to its contours, simulating cardiomegaly on chest skiagram.3 We report a case of thymolipoma presenting as an anterior mediastinal mass extending into both hemithoraces and causing collapse of the lower lobe of the left lung.
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Case Report
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A 25-year-old female presented in New York Heart Association functional class III with progressively increasing dyspnea on exertion of 6-months duration and persistent left-sided mild chest pain, particularly on exertion. Physical examination was unremarkable except for an increased area of cardiac dullness with diminished air entry in the lower zone of the left lung. A chest skiagram revealed a homogenous opacity involving the left hemithorax with normal inflation of the left upper lobe, a mediastinal shift to the right, and diffuse haziness in the right lower zone (Figure 1
). A contrast-enhanced computed tomography scan of the chest revealed a large mass of fat tissue density in the lower two thirds of the left hemithorax with extensions into the anterior mediastinum and the right hemithorax (Figure 2). Computed tomography-guided fine-needle aspiration cytology was consistent with the diagnosis of thymo-lipoma.
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Figure 1. Chest skiagram (posteroanterior view) showing homogenous opacity in the mediastinum and thorax with residual aeration of the left upper lobe of the lung. Inset (lateral view) showing a huge anterior mediastinal mass.
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Figure 2. Contrast-enhanced computed tomography chest scan showing an anterior mediastinal mass of fat tissue density with bilateral extension into the thorax.
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The tumor was excised en bloc through a median sternotomy combined with an extended left anterolateral thoracotomy (4th intercostal space), separating it from the adjacent pleurae and heart. The lower lobe of the left lung was collapsed due to compression by the massive tumor but readily reexpanded on positive-pressure ventilation intraoperatively. On gross examination, the tumor was well encapsulated, yellowish white, with a lobulated surface (Figure 3). It weighed 3.5 kg and measured 30 x 25 x 20 cm. On microscopic examination, a mixture of mature adipose tissue and thymic tissue characteristic of thymolipoma was seen (Figure 4). The patient had an uneventful postoperative recovery and was discharged after 9 days. At follow-up after 1 year, there was no clinical or radiological evidence of residual tumor or tumor recurrence.
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Figure 4. Photomicrograph showing a mixture of mature adipocytes and thymic tissue with occasional Hassle's corpuscles (arrow) (hematoxylin and eosin stain, original magnification x250).
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Discussion
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Whereas mediastinal lipomas of nonthymic origin are more common, thymolipoma is a very rare well-encapsulated benign anterior mediastinal tumour.4 The reported ages of the patients range from 4 to 54 years (mean age 22 years).5 Although the majority of such tumors are asymptomatic, the common clinical mani-festations attributed to its huge size can be dyspnea, cough, and paroxysmal tachycardia. Isolated instances of association with myasthenia gravis, aplastic anemia, and Graves disease are also known.6 Unlike the present case, 11 patients with myasthenia gravis due to cortical differentiation and active thymocyte proliferation have been reported.7
Grossly, the tumor is yellowish, soft, pliable, often lobulated with thin edges, and originates in the anterior mediastinum attached to the base of the heart by a vascular pedicle. These tumors usually attain huge size (68% weighing over 500 g, 23% over 2 kg, and 1 weighed over 12 kg).4 As the tumor enlarges it moulds and accommodates itself into the spaces between the lungs, heart, diaphragm, and anterior mediastinum. On chest skiagram, it may appear as a sharply circumscribed round or oval mediastinal density anterior to the base of the heart, simulating cardiomegaly. However, the thin periphery of a thymolipoma often appears more lucent than its thicker central portion and only well-penetrated films allow recognition of the true underlying cardiac and diaphragmatic shadows.3 As we found in our patient, a computed tomography scan of the chest can demonstrate a large sharply-circumscribed anterior mediastinal mass of diffuse fat density intermingled with small areas of soft tissue attenuation corresponding to adipose and thymic elements. This can suggest a preoperative diagnosis of thymolipoma in 91% of patients.8 Microscopically mature adipose tissue and unremarkable thymic tissue, well in excess of that normally expected for the patients' age group, is seen. Two cases of thymic liposarcoma, a malignant counterpart of thymolipoma have also been reported.9 Early surgical excision is recommended through a median sternotomy but it may require extended anterolateral thoracotomy depending upon the size of the tumor mass.
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References
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Lange I. Uber ein Lipom des Thymus. Zentralbl Allg Path Pathol Anat 1916;27:97–101.
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Yeh HC, Gordon A, Kirschner PA, Cohen BA. Computed tomography and sonography of thymolipoma. AJR 1983;140:1131–3.[Free Full Text]
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Teplick JG, Nedwich A, Haskin ME. Roentgenographic features of thymolipoma. AJR 1973;117:873–7.[Abstract]
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Moigneteau C, Cornet E. Thymolipoma. J Chir 1964; 94:509–14.
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Korhonen LK, Laustela E. Thymolipoma. J Thorac Cardiovasc Surg 1968;2:147–50.
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Otto HF, Loning TH, Lachenmayer L, Janzen RWC, Gurtler KF, Ficher K. Thymolipoma in association with myasthenia gravis. Cancer 1982;50:1623–8.[Medline]
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Sirpal YM, Chadha SK, Banerjee AK. Thymolipoma — a rare mediastinal tumour. Report of two cases and review of literature. Indian J Cancer 1995;32:23–6.[Medline]
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Rosado de Christenson ML, Pugatch RD, Moran CA. Thymolipoma: analysis of 27 cases. Radiology 1994; 193:121–6.[Abstract/Free Full Text]
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Havlicek F, Rosai J. A sarcoma of thymic stroma with features of liposarcoma. Am J Clin Pathol 1984;82:217–24.[Medline]
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Abstract
Introduction
