Ann Thorac Surg 2009;88:291-293. doi:10.1016/j.athoracsur.2008.12.037
© 2009 The Society of Thoracic Surgeons
Case Reports
Extralobar Sequestration in Anterior Mediastinum With Pericardial Agenesis
Mohammad Behgam Shadmehr, MDa,*,
Hamid Reza Jamaati, MD, FCCPb,
Bahare Saidi, MDa,
Mahmood Tehrai, MDc,
Mehrdad Arab, MDa
a Department of Surgery, Atieh Hospital, Shahrake Ghods, Tehran, Iran
b Department of Pulmonary Medicine, Day General Hospital, Tehran, Iran
c Department of Radiology, Day General Hospital, Tehran, Iran
Accepted for publication December 5, 2008.
* Address correspondence to Dr Shadmehr, Lung Transplantation Research Center, National Research Institute of Tuberculosis and Lung Disease (NRITLD), Masih Daneshvari Hospital, Shahid Beheshti University of Medical Sciences, Shahid Bahonar Ave, Darabad, Tehran, 19569-44413, Iran (Email: mbshadmehr{at}sbmu.ac.ir).
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Abstract
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We report a very rare case of extralobar sequestration and pericardial agenesis in a 22-year-old man. A computed tomographic (CT) scan demonstrated an anterior mediastinal mass. No aberrant artery was preoperatively identified. The patient underwent surgery with an impression of thymoma. An extralobar sequestration receiving its blood supply from the left pulmonary artery, accompanied with pericardial agenesis, was noted at the time of operation. The anterior mediastinum is an unusual site for extralobar sequestions. It is recommended to include extralobar sequestration in the differential diagnosis of anterior mediastinal masses, even if the aberrant artery is not recognized on the computed tomographic scan.
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Introduction
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Extralobar bronchopulmonary sequestration is a rare congenital lung tissue anomaly. It usually presents between the diaphragm and lower lobe of the lungs, and receives its arterial blood supply from the aorta. There has been reports of varied other locations, such as the mediastinal, intrapericardial, and intra-abdominal. Extralobar sequestration frequently accompanies other congenital anomalies [1, 2].
Herein we report a case of anterior mediastinal mass, which was operated on with the assumption of thymoma; however, it proved to be an extralobar sequestration associated with another rare congenital anomaly, pericardial agenesis.
A 22-year-old otherwise healthy man presented to us with a 6-month history of dry cough and vague chest pain. Physical examination was normal. He was previously sent for a computed tomography (CT) pulmonary angiography scan to rule out pulmonary embolism, which revealed no emboli; however, a hypodense anterior mediastinal mass was demonstrated (Fig 1). All other paraclinic evaluations were within normal limits. With a preoperative diagnosis of stage I thymoma, the patient underwent a median sternotomy.
On entrance, the heart was found to be located in the left pleural cavity because of a full anterior pericardial agenesis. The mass was not originating from the thymus gland. It was a mixed solid, cystic mass adherent to the main pulmonary artery (Fig 2). It was dissected meticulously and found to have a major vascular branch as well as some minor branches from the left main pulmonary artery right after its takeoff from the main pulmonary artery.
The main vascular branch was transected and suture ligated. The other branches were either cauterized or ligated. The mass was completely resected with no intraoperative bleeding.
On gross examination of the resected mass, bosselated gray-brown lung tissue measuring 7 x 5.5 x 3.5-cm was demonstrated. After sectioning, a well-defined, multi-loculated cystic lesion filled with gelatinous material (measuring 7 cm in greatest diameter) was noted. Inner wall of the cyst was smooth. Microscopic evaluation documented the diagnosis of bronchopulmonary sequestration.
On retrospective evaluation of the computed tomography angiographic scans, the anomalous artery supplying the anterior mediastinal mass was seen (Fig 3).
The patient has been doing well with no complications 1 year after surgery.
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Comment
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Bronchopulmonary sequestration is a congenital malformation, consisting of abnormal lung tissue with no attachment to the normal bronchopulmonary system. There are two variants: intralobar and extralobar sequestration. Extralobar sequestration constitutes 25% of sequestration cases and frequently presents within the first decade of life [3]. Unlike intralobar sequestration, which is located within the lung parenchyma, extralobar sequestraion is located outside the lung parenchyma, is covered by a separate pleural sac [3], and receives its blood supply from the abdominal or thoracic aorta, and in rare cases from the pulmonary artery [1].
Extralobar sequestration usually presents between the lower lobe of the lung and the diaphragm [1]. There have been very few reported cases of extralobar sequestration in the anterior mediastinum in adults [1, 4–6]. The association of extralobar sequestration with pericardial agenesis makes it an extremely rare presentation. We believe that no more than two cases of anterior mediastinal extralobar sequestrations with pericardial agenesis have already been reported in adults [5, 6].
Most of the time, the diagnosis of extralobar sequestration is challenging. Savic and colleagues [1] studied 133 patients with extralobar sequestration, and only six cases were preoperatively diagnosed. Spiral computed tomographic scans and computed tomographic angiograms are frequently used to detect this anomaly and identify the anomalous artery; however, if the aberrant artery is not visualized, bronchopulmonary sequestration should not be ruled out [3]. The unusual site of extralobar sequestration in the anterior mediastinum and the small size of the aberrant artery can make the diagnosis difficult for the unsuspecting radiologist, and misinterpretation as a thymoma or other pathologies, such as cystic adenomatoid malformation, bronchogenic cyst, and teratoma can occur [4].
It has been demonstrated that in more than 50% of cases, extralobar sequestraion accompanies other congenital anomalies [1, 2]. Whenever its diagnosis is suspected, investigation for other congenital anomalies is recommended.
Surgery is recommended in most cases. Significant bleeding has been reported when the feeding arteries were not recognized or were improperly ligated [4, 5, 7]. The safe resection of an extralobar sequestration in the anterior mediastinum requires meticulous dissection because of the potential feeding arteries from the main pulmonary artery. Not paying enough attention in this regard my lead to severe bleeding due to disruption of the branches from its base, and extension of the tearing over the thin wall of the pulmonary artery.
Despite its rarity, extralobar sequestion should be part of the differential diagnosis of anterior mediastinal masses, even if the feeding artery is not preoperatively visualized. Particular attention should be paid to precise ligation of the feeding arteries. Extralobar sequestrations are frequently associated with other congenital anomalies, pericardial agenesis is a likely associated finding with anterior mediastinal sequestrations.
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References
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- Savic B, Birtel FJ, Tholen W, Funke HD, Knoche R. Lung sequestration: report of seven cases and review of 540 published cases Thorax 1979;34:96-101.[Abstract/Free Full Text]
- Halkic N, Cuénoud PF, Corthésy ME, Ksontini R, Boumghar M. Pulmonary sequestration: a review of 26 cases Eur J Cardiothorac Surg 1998;14:127-133.[Abstract/Free Full Text]
- Ahmed M, Jacobi V, Vogl TJ. Multislice CT and CT angiography for non-invasive evaluation of bronchopulmonary sequestration Eur Radiol 2004;14:2141-2143.[Medline]
- Ke FJ, Chang SC, Su WJ, Perng RP. Extralobar pulmonary sequestration presenting as an anterior mediastinal tumor in an adult Chest 1993;104:303-304.[Abstract/Free Full Text]
- Datta G, Tambiah J, Rankin S, Herbert A, Lang-Lazdunski L. Atypical presentation of extralobar sequestration with absence of pericardium in an adult J Thorac Cardiovasc Surg 2006;132:1239-1240.[Free Full Text]
- Porte HL, Massouille DG, Lebuffe GR, Wurtz AJ. A unique congenital mediastinal malformation Ann Thorac Surg 2001;71:1703-1704.[Abstract/Free Full Text]
- Clements BS, Warner JO, Shinebourne EA. Congenital bronchopulmonary vascular malformations: clinical application of a simple anatomical approach in 25 cases Thorax 1987;42:409-416.[Abstract/Free Full Text]
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[Full Text]
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