MEDIASTINAL BRONCHOGENIC CYSTS OF ADULTS: Report of 5 cases

1. CH2 MEDIASTINAL BRONCHOGENIC CYSTS OF ADULTS: Report of 5 cases • Fouad, R. Saouab, D. Essaoufi, B. Radouane, S. Chaouir, T. Amil, • A. Hanine, J. El Fenni • Military Teaching Hospital MV Rabat - Morocco

2. INTRODUCTION • Bronchogenic cysts are one of the most common bronchopulmonary malformations. • Modern imaging techniques such as CT and MRI are useful for precise preoperative diagnosis. • However, despite advances in diagnostic imaging, the definitive diagnosis of a mediastinalbronchogenic cyst is histological.

3. The aim of our study is to: • Recall the etiopathogenesis, epidemiological and clinical data of mediastinalbronchogenic cysts • Illustrate the imaging appearance in different modalities of exploration

4. MATERIALS AND METHODS • Retrospective study of 5 cases of mediastinalbronchogenic cysts in adults explored in our service over a period of 9 years. • Chest radiography and chest CT were performed in all cases; MRI was realised in only one case. • Surgical resection was performed in all patients. • Histopathological study confirmed the diagnosis

5. RESULTS • We found in our series 4 women and 1 man with an average age of 50 years. • No pathologic history • The cystwas discovered incidentally in 3 cases on the chest radiography; by dyspnea in one case and a chronic cough in other case. • The cyst was located in the middle mediastinum in 4 cases and in the anterior mediastinum in 1case. • The mean diameter of the cyst was 6.7 cm.

6. RESULTS • Pathological examination of the surgical specimen led to the diagnosis in all cases. • The postoperative course was unremarkable. • The subsequent evolution was favorable

7. Case n° 1 Posterior anterior and lateral chest x-ray: infero-lateral opacity of the middle and inferior mediastinum Contrast material-enhanced CT scan : a well-circumscribed cyst in contact with the inferior vena cava

8. Case n° 2 Chest radiograph: homogeneous  anterior right mediastinal mass Axial contrast-enhanced chest CT scan (mediastinal window settings): a well-circumscribed homogenus cyst In the right latero-tracheal lodge

9. Axial T1 and T2-weighted MR images shows that the lesion is of similar signal intensity to that of CSF, which suggests a cyst.

10. Case n° 3 Chest radiograph: homogeneous  retrocardiac mass Axial contrast-enhanced chest CT scan (mediastinal window settings) : a well-circumscribed left cyst in the middle and posterior mediastinum

11. Case n° 4 Chest radiograph: homogeneous right middle mediastinal mass Axial contrast-enhanced chest CT scan (mediastinal window settings) : a well-circumscribed cyst in the middle mediastinum

12. Case n° 5 chest radiograph: homogeneous right paracardiac mass with pleural effusion Axial contrast-enhanced chest CT scan (mediastinal window settings): a well-circumscribed hyper dense cyst in the middle mediastinum extended to posterior mediastinum,with pleural effusion.

13. DISCUSSION

14. Embryological recall • Bronchogenic cysts result from abnormal budding of the ventral foregut that occurs between the 26th and 40th days of gestation. • They are lined with pseudostratified columnar respiratory epithelium, and their walls usually contain cartilage, smooth muscle, and mucous gland tissue(1). • They may be filled with clear, serous fluid or thick, mucoid material.

15. Epidemiology • They may occur in any part of the mediastinum, but most are near the tracheal carina in the middle or posterior mediastinum. • Mediastinal bronchogenic cysts are sometimes associated with other congenital pulmonary malformations such as sequestration and lobar emphysema(2). • They may undergo an abrupt increase in size as a result of hemorrhage or infection

16. Clinical data • The majority are asymptomatic, but they may occasionally cause symptoms secondary to compression of adjacent structures. • These symptoms include chest pain, cough, dyspnea, fever, and purulent sputum(3).

17. Imaging findings 1. Chest radiographs: • It is usually adequate for detectinglarger mediastinal masses as a homogeneousopacity; • But, it is limited in the tissue characterization of the lesion

18. Imaging findings  2. CT scan: • It is used to characterize the mass and clarify its relationship to adjacent mediastinal structures. • It is characteristic when the lesion demonstrates a homogeneous fluid attenuation mass with a thin or imperceptible wall.

19. Imaging findings ! 2. CT scan: • The attenuation value is dependent on the contents of the cyst. • It can vary from water attenuation to soft-tissue attenuation. • The value can be more than 100 HU owing to a high protein level or calcium oxalate in the mucoid cyst(4,5). • Air within the cyst is uncommon and suggestive of secondary infection and communication with the tracheobronchial tree. • Calcification occurs occasionally in the wall or within the cyst contents.

20. Imaging findings 3. MRI: • It is helpful in cases where the cystic nature of the mass is not apparent on CT. • MRI should always be indicated in cases of posterior mediastinal mass to assess the relationship with the spine

21. Imaging findings 3. MRI: • The cystic nature of the mass is confirmed by the high signal intensity on T2-weighted images regardless of the cyst contents. • At T1-weighted images, variable patterns of signal intensity are seen because of variable cyst contents and the presence of protein, hemorrhage, or mucoid material(6). • A fluid-fluid level within the bronchogenic cyst may be seen(7).

22. Differential diagnosis • It arises with other cystic lesions of the mediastinumincluding : • Congenital benign cysts : duplication cysts, neurenteric cysts, meningocele, pericardial cysts, thymic cysts, cystic teratoma, and lymphangioma. • Mediastinal abscess • Pancreatic pseudocyst • Clinical history, anatomic position, associated abnormalities and imaging semiology allow correct diagnosis in many cases.

23. Treatment • The choice of treatment is controversial. • Some authors advocate surgical excision of all cysts given their tendency to become infected or rarely, to undergo malignant transformation(8). • Increasingly, these lesions are treated with transbronchial or percutaneous aspiration under CT guidance to both confirm the diagnosis and to treat them. • Small lesions can be followed.

24. Intraoperative appearance of bronchogenic cyst Intraoperative aspiration of bronchogenic cyst.

25. CONCLUSION • A cystic mediastinal mass with a thin or imperceptible wall in a subcarinal location should be a bronchogenic cyst. • In cases where the cystic nature is not apparent on CT, the high signal intensity on T2-weighted images should confirm the cystic nature.

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