Ann Thorac Surg 2007;83:1528-1530
© 2007 The Society of Thoracic Surgeons
Case Reports
Posterior Mediastinal Chondromatous Hamartoma
Suad Gholoum, MDa,
Richard Fraser, MDb,
Lorenzo E. Ferri, MDa,*
a Division of Thoracic Surgery, McGill University, Montréal, Québec, Canada
b Department of Pathology, McGill University, Montréal, Québec, Canada
Accepted for publication September 14, 2006.
* Address correspondence to Dr Ferri, 1650 Cedar Avenue, Room L9–113, Montréal, QC H3G 1A4, Canada (Email: lorenzo.ferri{at}muhc.mcgill.ca).
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Abstract
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A posterior mediastinal mass was found incidentally in a 70-year-old woman during a work-up for an early breast cancer. Computed tomography of the chest showed a well-circumscribed mass near the left subclavian artery and proximal descending aorta. A left video assisted thorascopic excision of the posterior mediastinal mass was performed. Pathologic examination showed it to be a chondromatous hamartoma, representing a very unusual location for this type of tumor.
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Introduction
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Chondromatous hamartomas are relatively common pulmonary abnormalities, accounting for about 75% of all benign lung tumors. They are believed to derive from perichondrial mesenchymal cells. Although most are intimately related to an airway and are located in the parenchyma, rare examples are found in an endobronchial location [1]. We report a rare case of an otherwise typical chondromatous hamartoma situated in the posterior mediastinum.
A 70-year-old woman known for a left breast carcinoma treated by lumpectomy in 2005 was found to have a double convex contour of the aortic notch on a routine chest roentgenogram. A follow-up computed tomography examination to further evaluate the mass and to rule out an aortic aneurysm showed a 3.5-cm heterogeneous, noncalcified mass in the posterior mediastinum immediately cephalad to the proximal descending aorta (Fig 1).
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Fig 1. A chest computed tomography scan reveals a well-circumscribed heterogeneous mass in the posterior mediastinum adjacent to the superior border of the aortic arch (arrow).
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A left video-assisted thoracoscopic excision of the mass was performed. Access was gained through three ports (one 12 mm and two 5 mm), and a 5-mm, 30-degree video scope provided visualization. After division of moderate adhesions between the visceral and parietal pleura, the upper lobe was easily retracted from the superior mediastinum to expose the mass. A well-circumscribed tumor was adherent to the adventitia of the proximal descending aorta (Fig 2). The adhesions were divided with endoscopic harmonic shears. The patient had an uneventful postoperative course and was discharged from the hospital on the second postoperative day.
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Fig 2. Endoscopic view of the left mediastinum. The tumor (T) can be appreciated posterior to the left subclavian artery (LSCA) adherent to the superior aspect of the proximal descending aorta (Ao), with no attachment to the visceral pleura of the retracted lung (L).
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Histologic examination showed typical features of a pulmonary chondromatous hamartoma consisting of lobules of mature cartilaginous tissue separated by variable amounts of fat (Fig 3A). A small amount of compressed lung parenchyma bordered by pleural tissue was evident around the periphery of the tumor and confirmed by positive immunohistochemical reaction of residual alveolar epithelial cells for thyroid transcription factor-1 and of pleural mesothelial cells for calretinin (Fig 3B).
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Fig 3. (Left) Histologic appearance of tumor shows fat and cartilage. (60x magnification.) (Right) Immunohistochemical reaction to calretinin shows mesothelial cell layer at periphery of tumor. (150x magnification.)
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Comment
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About 20% of all mediastinal tumors arise in the posterior compartment, with neurogenic tumors being the most common [2]. Given the close proximity to the aorta in the present case, an aorticopulmonary paraganglioma was the working diagnosis. Surprisingly, a chondromatous hamartoma was found on histologic examination, representing a very unusual location for this type of tumor.
Hamartomas are the most common benign tumor of the lung, representing about 5% to 8% of all solitary pulmonary nodules. They occur more often in men, and the incidence is highest in the sixth decade. Several theories have been postulated to explain their nature, the most widely believed being that they represent a congenital malformation or a benign neoplasm ("mesenchymoma") with cartilaginous differentiation. The observations that they can increase in size on serial roentgenograms, that they are rare in children, and that they can show cytogenetic abnormalities similar to those of other soft tissue neoplasms suggest that they are in fact benign neoplasms [3].
Almost all chondromatous hamartomas are located in the lung parenchyma; approximately 90% of these are peripheral and 10% are located centrally. Rare examples are situated within the lumen of a proximal bronchus. The present case demonstrates a particularly unusual location. How the tumor came to reside in the mediastinum is open to speculation.
Theoretically, the hamartoma could have arisen within a "pulmonary rest" in the mediastinum. However, the presence of a layer of compressed pulmonary tissue and pleura surrounding the tumor suggests that an intraparenchymal hamartoma migrated across the visceral pleura into the mediastinum. Such migration within the lung is uncommon, but well described with foreign bodies [4] and calcified necrotic material within peribronchial lymph nodes (resulting in broncholithiasis) [5], and is presumably related to the cyclic motion of respiration. Indeed, penetration of a hamartoma through the visceral pleura with adhesion to the mediastinal pleura has been reported [6]. The present case represents a slightly greater degree of migration that resulted in complete localization within the mediastinum.
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References
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- van den Bosch JM, Wagenaar SS, Corrin B, Elbers JR, Knaepen PJ, Westermann CJ. Mesenchymoma of the lung (so called hamartoma): a review of 154 parenchymal and endobronchial cases Thorax 1987;42:790-793.[Abstract/Free Full Text]
- Duwe BV, Sterman DH, Musani AI. Tumors of the mediastinum Chest 2005;128:2893-2909.[Medline]
- Fletcher JA, Pinkus GS, Donovan K, et al. Clonal rearrangement of chromosome band 6p21 in the mesenchymal component of pulmonary chondroid hamartoma Cancer Res 1992;52:6224-6228.[Abstract/Free Full Text]
- Hilman BC, Kurzweg FT, McCook Jr WW, Liles AE. Foreign body aspiration of grass inflorescences as a cause of hemoptysis Chest 1980;78:306-309.[Medline]
- Fraser R. BroncholithiasisIn: Fraser RS, Muller N, Coleman N, Pare PD, editors. Fraser and Pare’s diagnosis of diseases of the chest. 4th ed.. Philadelphia, PA: W.B. Saunders; 1999. pp. 2287.
- Tomiyasu M, Yoshino I, Suemitsu R, Shoji F, Sugimachi K. An intrapulmonary chondromatous hamartoma penetrating the visceral pleura: report of a case Ann Thorac Cardiovasc Surg 2002;8:42-44.[Medline]
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Abstract
Introduction
