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Intrapericardial bronchogenic cyst:

Assessment with magnetic resonance imaging and transesophageal echocardiography

      Introduction

      A bronchogenic cyst, the most common type of intrathoracic foregut cyst, arises from an abnormality of tracheobronchial tree budding. Lined by columnar respiratory epithelium, these cysts may arise from many locations including the pericarinal, paratracheal, and intrapulmonary regions. Rarely, these cysts are identified in unusual locations, making diagnosis challenging. We present a case where a bronchogenic cyst is discovered within the pericardium of a middle-aged women presenting with chest pain, dyspnea on exertion, and shortness of breath. Imaging, surgical intervention, and pathologic specimens provide a complete overview of this unusual case. A review of the literature, including developmental characteristics, pathology, symptomatology, and radiologic features of bronchogenic cysts is also provided.

      Case report

      A 49-year-old Caucasian woman was admitted to an outside hospital with complaints of shortness of breath, pleuritic chest pain, and dyspnea on exertion. Her past medical history was significant only for an isolated bout of pleural and pericardial effusion 8 years ago, presumed to be of viral etiology, and treated successfully with pericardiocentesis (producing a sanginous fluid containing no organisms or malignant cells) and oral steroids. An echocardiogram later that year was reported to be normal with the exception of mild mitral valve prolapse.
      In the emergency room, physical examination was unremarkable except for mild respiratory distress. Standard blood chemistries and cell counts were within normal limits. A chest radiograph was obtained and was negative. Blood gases demonstrated mild hypoxemia Math Eq and the patient was sent for ventilation/perfusion imaging. This study revealed a mismatched perfusion defect in the right upper lobe, suspicious for acute pulmonary embolus. Heparin was begun, and subsequent pulmonary angiography proved negative.
      The patient remained stable until the day of transfer to Johns Hopkins when she developed upper extremity, chest, and neck edema, and moderate cyanosis. An echocardiogram revealed a large, echogenic mass with a fluid-fluid level filing or compressing almost the entire left atrium with marked superior vena cava compression and compression of the right pulmonary veins. Magnetic resonance imaging (MRI) was obtained and demonstrated a 7-cm mass in the left atrium probably arising from the posterior and superior aspect of the interatrial septum (Figure 1). The mass showed high signal on T2-weighted images. Near complete compression of the superior vena cava was noted.
      Figure thumbnail gr1a
      Figure 1A 49-year-old woman with an intrapericardial bronchogenic cyst. (A) Coronal T1-weighted MR images demonstrate a large mass arising from the interatrial septum extending into the left atrium with compression of the superior vena cava. Marked compression of the left atrium is also appreciated. (B) Axial T1-weighted MR image demonstrate a fluid-fluid level within the mass. (C) Axial T2-weighted MR image with fat saturation demonstrate high signal intensity within the mass. (D) Transesophageal echocardiogram demonstrates a large cystic mass compressing the entire left atrium (LA). A fluid-fluid level within the mass is also appreciated. The aorta is identified (A). (E) Histologic specimen reveals fragments of benign respiratory mucosal lined cyst consistent with bronchogenic cyst
      Figure thumbnail gr1b
      Figure 1A 49-year-old woman with an intrapericardial bronchogenic cyst. (A) Coronal T1-weighted MR images demonstrate a large mass arising from the interatrial septum extending into the left atrium with compression of the superior vena cava. Marked compression of the left atrium is also appreciated. (B) Axial T1-weighted MR image demonstrate a fluid-fluid level within the mass. (C) Axial T2-weighted MR image with fat saturation demonstrate high signal intensity within the mass. (D) Transesophageal echocardiogram demonstrates a large cystic mass compressing the entire left atrium (LA). A fluid-fluid level within the mass is also appreciated. The aorta is identified (A). (E) Histologic specimen reveals fragments of benign respiratory mucosal lined cyst consistent with bronchogenic cyst
      Figure thumbnail gr1c
      Figure 1A 49-year-old woman with an intrapericardial bronchogenic cyst. (A) Coronal T1-weighted MR images demonstrate a large mass arising from the interatrial septum extending into the left atrium with compression of the superior vena cava. Marked compression of the left atrium is also appreciated. (B) Axial T1-weighted MR image demonstrate a fluid-fluid level within the mass. (C) Axial T2-weighted MR image with fat saturation demonstrate high signal intensity within the mass. (D) Transesophageal echocardiogram demonstrates a large cystic mass compressing the entire left atrium (LA). A fluid-fluid level within the mass is also appreciated. The aorta is identified (A). (E) Histologic specimen reveals fragments of benign respiratory mucosal lined cyst consistent with bronchogenic cyst
      Figure thumbnail gr1d
      Figure 1A 49-year-old woman with an intrapericardial bronchogenic cyst. (A) Coronal T1-weighted MR images demonstrate a large mass arising from the interatrial septum extending into the left atrium with compression of the superior vena cava. Marked compression of the left atrium is also appreciated. (B) Axial T1-weighted MR image demonstrate a fluid-fluid level within the mass. (C) Axial T2-weighted MR image with fat saturation demonstrate high signal intensity within the mass. (D) Transesophageal echocardiogram demonstrates a large cystic mass compressing the entire left atrium (LA). A fluid-fluid level within the mass is also appreciated. The aorta is identified (A). (E) Histologic specimen reveals fragments of benign respiratory mucosal lined cyst consistent with bronchogenic cyst
      Figure thumbnail gr1e
      Figure 1A 49-year-old woman with an intrapericardial bronchogenic cyst. (A) Coronal T1-weighted MR images demonstrate a large mass arising from the interatrial septum extending into the left atrium with compression of the superior vena cava. Marked compression of the left atrium is also appreciated. (B) Axial T1-weighted MR image demonstrate a fluid-fluid level within the mass. (C) Axial T2-weighted MR image with fat saturation demonstrate high signal intensity within the mass. (D) Transesophageal echocardiogram demonstrates a large cystic mass compressing the entire left atrium (LA). A fluid-fluid level within the mass is also appreciated. The aorta is identified (A). (E) Histologic specimen reveals fragments of benign respiratory mucosal lined cyst consistent with bronchogenic cyst
      Open biopsy was then performed and upon opening the pericardium, the surgeons saw a “tense and hard” mass that on incision, produced a large amount of chylus-appearing fluid with some mucoid component. Suctioning of the fluid revealed a large cyst that had been compressing the left atrium and superior vena cava. Once decompression of the cyst was achieved, all cardiac structures returned to their normal positions. The cyst fluid and cyst wall were submitted to pathology. On microscopic examination, the cyst wall tissue revealed fragments of benign respiratory mucosal-lined cyst, consistent with bronchogenic cyst. All specimens were negative for tumor. The patient made a uneventful recovery, and was discharged 9 days after surgery.

      Discussion

      In 1948, Maier reported the clinical and pathologic features of bronchogenic cysts (
      • Maier H.C.
      Bronchogenic cyst of the mediastinum.
      ). These relatively rare developmental anomalies can occur at any point along the tracheobronchial tree, with the most common site near the carina. The location of bronchogenic cysts often determines their content. These cysts may be detected incidentally on plain chest radiographs or they could present as an emergent, life-threatening situation.
      Bronchogenic cysts are often present without symptoms and are detected incidentally on chest radiographs (
      • Defossez S.M.
      • Deluca S.A.
      Bronchogenic cysts.
      ). These cysts have been reported in neonates as well as adults. Dabbs et al. in 1957 reviewed 20 cases of bronchogenic cysts and found “no striking sex predilection,” (
      • Dabbs C.H.
      • Berg Jr, R.
      • Peirce II, E.C.
      Intrapericardial bronchogenic cysts report of two cases and probably embryologic explanation.
      ) but a majority of cases in young people. Defossez and Deluca reported in 1989 that they found a higher incidence of bronchogenic cysts in males and an increased incidence in Yemenite Jews (
      • Defossez S.M.
      • Deluca S.A.
      Bronchogenic cysts.
      ).
      Bronchogenic cysts are developmental anomalies that occur during early fetal development. The foregut branches into dorsal and ventral segments, with the dorsal segment eventually becoming the esophagus and the ventral segment becoming the tracheobronchial tree. The stage of development at which the abnormality called a bronchogenic cyst occurs is the determining factor of its location. These cysts can arise in the mediastinum or within the pulmonary parenchyma, and, rarely, below or within the diaphragm. Typically, bronchogenic cysts are thin-walled and lined with ciliated, mucus-secreting columnar epithelium. When a cyst is located in the subcarinal region, infection is rare, and it seldom communicates with the tracheobronchial tree. However, when there is communication with the tracheobronchial tree, infection is more likely, and the result is often an air-filled or pus-filled cyst or an air-fluid level.
      In neonates, bronchogenic cysts may suddenly become very large because of a check-valve mechanism. There have also been reports of giant intrapericardial bronchogenic cysts in adults (
      • Gomes M.N.
      • Hufnagel C.A.
      Intrapericardial bronchogenic cysts.
      ).
      In a review of a series of 42 patients, Suen et al. found that approximately 50% of all patients had pain substernally, in the shoulder, in the lateral chest, or between the scapulae (
      • Suen H.-C.
      • Mathisen D.J.
      • Grillo H.C.
      • LeBlanc J.
      • McLoud T.C.
      • Moncure A.C.
      • Hilgenberg A.D.
      Surgical management and radiological characteristics of bronchogenic cysts.
      ). Pain was the most common symptom, followed by cough, fever, dysphagia, purulent sputum, hemoptysis, and shortness of breath.
      The literature reports widely varying appearances of bronchogenic cysts, depending on location, size, and imaging method. While these cysts can be detected on plain films further characterization is indicated to differentiate between bronchogenic cyst and teratoma.
      Echocardiography has been used to assess cardiac and paracardiac mass lesions. However, computed tomography (CT) and, particularly, MRI, provide the same information as echocardiography and is noninvasive. Menegus et al. reported the results of MRI in seven patients whose echocardiograms demonstrated sessile atrial tumors (
      • Menegus M.A.
      • Greenberg M.A.
      • Spindola-Franco H.
      • Fayemi A.
      Magnetic resonance imaging of suspected atrial tumors.
      ). These authors concluded that MRI is more specific for diagnostic purposes than echocardiography.
      In a 1993 report examining the MRI characteristics of bronchogenic cysts, Nakata et al. reviewed MRI and CT finding in eight patients (
      • Nakata H.
      • Egashira K.
      • Watanabe H.
      • Nakamura K.
      • Onitsuka H.
      • Murayama S.
      • Murakami J.
      • Masuda K.
      MRI of bronchogenic cysts.
      ). They found that all the cysts in their study revealed homogeneous high signal intensity on T2-weighted images, of round or ovoid shape, and well-demarcated from surrounding structures. None of the cysts in their series enhanced after contrast injection.
      Both Nakata and Marin et al. (
      • Marin M.L.
      • Romney B.M.
      • Franco K.
      • Grimes M.M.
      • Smith C.
      Bronchogenic cyst a case report emphasizing the role of magnetic resonance imaging.
      ) reported that CT can be misleading because of equivocal cyst density readings. In Marin’s case report, the authors emphasize the importance of characterizing the nature of the lesion. CT could not definitely characterize this lesion as a simple fluid-containing structure. The intense signal on T2-weighted MR images strongly indicated the diagnosis of a fluid-filled structure.
      Recently, several authors have reported on MRI of a fluid-fluid level in mediastinal bronchogenic cysts (
      • Bargalló J.
      • Luburich P.
      • Garcia-Barrionuevo J.
      • Sanchez-Gonzalez M.
      Fluid-fluid level in bronchogenic cysts.
      ). Lyon and McAdams (
      • Lyon R.D.
      • McAdams H.P.
      Mediastinal bronchogenic cyst demonstration of a fluid–fluid level at MR imaging.
      ) suggested in their report that a fluid-fluid level on MRI is unequivocal proof that a lesion is cystic. In their case report, a large mass above the carina was detected on plain films. CT showed a nonenhancing mass between the trachea and the esophagus.
      MR at 1.5T on T1-weighted images demonstrated a fluid-fluid level within the mass. T2-weighted images showed very hyperintense fluid; however, neither of the fluid layers had signal intensities consistent with lipid or hemorrhage. When the patient was operated on to remove the cyst, no blood products were found and triglyceride levels were normal. The authors suggest that the fluid-fluid level in this case was due to a dependent layer of proteinaceous material within the cyst. A similar case was reported by Bargalló et al., who commented on the nature of the fluid-fluid level in these cysts (
      • Marin M.L.
      • Romney B.M.
      • Franco K.
      • Grimes M.M.
      • Smith C.
      Bronchogenic cyst a case report emphasizing the role of magnetic resonance imaging.
      ).

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