Ann Thorac Surg 2010;89:304-305. doi:10.1016/j.athoracsur.2009.06.046
© 2010 The Society of Thoracic Surgeons
Case Reports
Leiomyomatous Hamartoma of the Posterior Mediastinum
Benoit Jacques Bibas, MDa,
Ricardo Mingarini Terra, MDa,*,
Angelo Fernandez, MDa,
Christina Shiang, MDb,
Paulo Manuel Pêgo-Fernandes, MDa,
Fabio Biscegli Jatene, MDa
a Division of Thoracic Surgery, Hospital das Clínicas, University of São Paulo Medical School, São Paulo, Brazil
b Division of Pathology, Hospital das Clínicas, University of São Paulo Medical School, São Paulo, Brazil
Accepted for publication June 9, 2009.
* Address correspondence to Dr Terra, Al Fernão Cardim 161, Ap. 61, São Paulo, 01403-020, Brazil (Email: rmterra{at}uol.com.br).
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Abstract
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A posterior mediastinal mass was found in a 72-year-old man who complained of progressive shortness of breath. Computed tomography of the thorax showed a well-defined, heterogenous mass measuring 9.5 x 4.0 x 3.0 cm, located in the right costovertebral angle. Complete surgical resection was accomplished through a right posterolateral thoracotomy. The final diagnosis was a leiomyomatous hamartoma of the posterior mediastinum. This is an unusual location for this type of tumor, and it has rarely been reported in the literature.
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Introduction
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Hamartomas are common pulmonary lesions, accounting for 8% of all pulmonary neoplasms [1]. The lesions are usually well circumscribed on radiographic images and are normally between 1 and 2 cm in diameter, although larger tumors are occasionally seen. Calcification is common and better visualized in computed tomography (CT) scans [1]. Most hamartomas are located in the periphery of the pulmonary parenchyma, but 1% to 20% may occur as endobronchial lesions and cause symptoms related to bronchial obstruction [1, 2]. We present a patient with a leiomyomatous hamartoma located in the posterior mediastinum. This location is atypical and rarely reported for this type of tumor.
A previously healthy 72-year-old man presented to his regular physician for a routine consultation in which he complained of progressive dyspnea in the last year. He had no history of pulmonary diseases and was a nonsmoker. Lung sounds were clear, except for decreased breath sounds and decreased fremitus at the right base, without egophony. Laboratory test results revealed no abnormalities.
A chest roentgenogram showed a mass in the right hemithorax. CT depicted a large, heterogeneous, partially calcified, and well-defined mass located in the right costovertebral region (Fig 1). There was no sign of extension into the spinal canal or adjacent structures. Radiographic findings were compatible with a neurogenic tumor of the mediastinum or a fibrous tumor of the pleura. Based on that hypothesis, it was decided not to biopsy the lesion.
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Fig 1. Computed tomography of the thorax shows a well-defined mass measuring 9.5 x 4.0 x 3.0 cm located in the right costovertebral region. The vascular supply (arrow) to the mass has its origin in the mediastinum.
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The patient was operated on through a right posterolateral thoracotomy. A large, immobile, encapsulated, and lobulated mass was evident in the costovertebral region. It was fully covered with mediastinal pleura and had a rich vascular supply that had its origin in the mediastinum. The lesion compressed the right lower lobe, but with no evidence of local invasion. Complete en bloc resection of the tumor was achieved after careful dissection. The patient had an uneventful recovery and was discharged from the hospital on postoperative day 4.
Gross examination revealed a circumscribed, tan-colored mass measuring 9.5 x 4.0 x 3.0 cm and weighing 110 g. Histologically, it showed a proliferation of spindle-shaped smooth muscle growing in between slit-like spaces lined by cytologically bland, flattened, cuboidal cells. These epithelial lining cells are type 2 pneumocytes that stain for thyroid transcription factor-1. Clefts of respiratory-type epithelium associated with mucinous gland hyperplasia were also seen focally (Fig 2). CD-34 stain was negative.
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Fig 2. (A) Histology specimens show smooth muscle proliferation around slit-like spaces lined by pneumocytes. Intraalveolar respiratory macrophages are also seen (hematoxylin-eosin stain, original magnification x200). (B) Clefts are lined by respiratory-type epithelium (hematoxylin-eosin stain, original magnification x200). (C) Immunohistochemistry shows thyroid transcription factor-1 positivity in the alveolar-like space lining (original magnification x200). (D) Strong positivity for desmin in the spindle cell proliferation (original magnification x100).
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The final diagnosis was a leiomyomatous hamartoma. It was classified as a hamartomatous lesion because of its varying proportions of mesenchymal tissue and respiratory-type epithelium. The mesenchymal component, represented by spindle cells, is actually smooth muscle tissue because of desmin and smooth muscle actin positivity.
The patient is alive and without signs of recurrence 4 years after the operation.
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Comment
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Mediastinal tumors are often asymptomatic and usually detected by chest roentgenogram. When symptoms are present, the most common are chest pain, cough, dyspnea, and superior vena cava syndrome [3]. Approximately 25% of the mediastinal neoplasms occur in the posterior compartment, and 75% of these tumors are of neurogenic origin [4]. Other less common masses of the posterior mediastinum include tumors of mesenchymal origin and gastroenteric cysts [3, 4].
Hamartomas may be defined as a disorganized focus or an overgrowth of mature tissues found normally at the location of the lesion. With low capacity of growth and benign behavior, the implicated tissues proliferate in a disorganized manner, and its descriptive name depends on the predominant tissue [5]. Therefore, hamartomas may be designated as rhabdomyomatous, neurovascular, lymphatic, fatty, and so forth [5]. The histology of the pulmonary lesions reveals a predominant chondroid differentiation in 80% of the cases, with fibroblastic (12%), fatty (5%), and osseous (3%) differentiation comprising the rest [6]. Leiomyomatous hamartomas are particularly rare, and the presence of smooth muscle predominates over other possible components [5].
The location of the hamartoma in this patient is unusual. Although extremely rare, a hamartoma of chondromatous differentiation in the posterior mediastinum was reported by Gholoum and colleagues [7]. In the resected specimen, a small amount of compressed lung parenchyma bordered by pleural tissue was evident around the periphery of the tumor and confirmed by immunohistochemical analysis. The authors postulated that this layer of pulmonary parenchyma surrounding the lesion could indicate that an intraparenchymal hamartoma had migrated across the visceral pleura into the mediastinum.
Such migration within the lung is uncommon but is well described with foreign bodies and calcified necrotic material within peribronchial lymph nodes (resulting in broncholithiasis), and is probably related to the cyclic motion of respiration [7]. Indeed, penetration of pulmonary hamartoma through the visceral pleura with adhesion to the mediastinal pleura has been reported [8]. Whether mediastinal hamartomas may be described as primary mediastinal tumors or lesions that have migrated through the pulmonary parenchyma is a question to be answered and open to speculation. The case reported here favors the hypothesis of a primary mediastinal mass because the tumor was fully covered with mediastinal pleura and its vascular supply clearly originated from the mediastinum. To our knowledge, this is only the second report of a posterior mediastinal hamartoma.
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References
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- Shrager JB, Kaiser LR. Benign lung tumorsIn: Patterson GA, Cooper JD, Deslauriers J, Lerut A, Luketich JD, Rice TW, editors. Pearson's thoracic & esophageal surgery. 3rd ed.. Philadelphia: Churchill Livingstone; 2008. pp. 691-698.
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- Nava-Villalba M, Ocampo-Acosta F, Seamanduras-Pacheco A, Aldape-Barrios BC. Leiomyomatous hamartoma: report of two cases and review of the literature Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;105:e39-e45.[Medline]
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- Gholoum S, Fraser R, Ferri LE. Posterior mediastinal chondromatous hamartoma Ann Thorac Surg 2007;83:1528-1530.[Abstract/Free Full Text]
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Abstract
Introduction
