Tumours and cysts of the mediastinum

Non-Neoplastic Mediastinal Cysts

Primary mediastinal cysts are infrequent lesions that can arise from a variety of mediastinal organs or structures. Most of these are congenital in origin and incidental findings during investigations for unrelated conditions. Histologically, the cysts may be composed of various tissues, including bronchogenic, pericardial, thymic, enteric, Müllerian, lymphatic, and parathyroid types. Mediastinal cysts typically demonstrate a benign clinical course and patients are cured after complete surgical resection. In this review, the embryogenesis, clinical, radiologic, and pathologic characteristics of non-neoplastic mediastinal cysts are examined with discussion of the role of immunohistochemistry and the most pertinent differential diagnosis.

[Mediastinal cysts: clinical approach and treatment]

Mediastinal cysts (MC), mainly from embryonic origin, are benign and rare malformative lesions, gathering several varieties according to tissue origin. Diagnosis is mostly obtained thanks to tomodensitometry performance and sometimes by magnetic resonance imaging. It may be more difficult in some atypical topographies and in case of bulky MC. The most frequent, springing from division abnormality from embryonic foregut ("foregut cysts" in English literature), are primarily bronchogenic cysts (50 to 60 % of MC), which are symptomatic in 30 to 80 % of cases. Coelomic cysts, lined by a mesothelium, result from embryologic abnormality by incomplete fusion of mesenchymal coelomic lacunae. Rarely symptomatic, excepted in cases of very large cysts, they are mainly pleuropericardic cysts (PPC) that represent 30 % of MC. Thymic cysts, around 15 % of MC, are most often asymptomatic. Cystic lymphangiomas (CL) are congenital lymphatic malformations more frequent and symptomatic in children. Diagnosed in older patients, they are most often acquired and asymptomatic. The only radical and definitive treatment is complete surgical resection of the cyst. It allows suppression of symptoms, procurement of a formal diagnosis and prevention of complications. This resection, generally indicated for all symptomatic cysts, large-sized even asymptomatic and in case of non formal diagnosis, is now recommended for all kinds of cysts except for asymptomatic PPC. This strategy is justified considering morbidity and mortality rising rates in patients treated by surgical resection at time of local complications of the cyst. Surgery is commonly performed by videothoracoscopy or by video-assisted mini-thoracotomy, mainly for PPC and CL. The more conventional thoracotomy is performed in surgery for cysts, which are adhesive to nearby structures. PPC just need a simple follow-up, and surgery is required only in case of symptoms and increasing size. In total, surgical indications for MC are large and accepted because of null postoperative mortality and very low rate of morbidity thanks to mini-invasive surgery. This militates for early surgery, without waiting for cystic complications leading to peroperative difficulties and increasing risks. This review presents the characteristics of those different cysts and the strategies currently acknowledged for the treatment.

Cystic lesions of the mediastinum

Cysts of the mediastinum comprise a relatively diverse group of lesions that include neoplastic and nonneoplastic constituents, the latter of which are largely congenital in nature. Therefore, a grasp of their clinicopathologic characteristics is bolstered by knowledge of which tumors in the chest may undergo cystic change, as well as the embryologic development of the thoracic organs. That information, as well as radiological and pathologic features of these lesions, is discussed in this review.

Primary mediastinal leiomyoma

An elderly woman was seen with a left mediastinal mass in the region of the aortic arch on chest roentgenography. Further imaging with computed tomography, angiography, and magnetic resonance demonstrated a highly vascular neoplasm adjacent to the aortic arch. Pathological analysis of the resected specimen showed a leiomyoma. A brief review of the 10 previous reported cases of primary mediastinal leiomyoma is provided.

Central bronchogenic cyst: treatment by extrapleural percutaneous aspiration

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Thymoma and myasthenia gravis in a 4-year-old child. Case report and review of the literature

Thymomas are exceedingly rare in the first 20 years of life, and only a few well-documented cases are present in the literature. Thymomas in adults are commonly associated with other diseases, the most frequent being myasthenia gravis (MG). However, this association has been reported not to occur in childhood. The authors report the case of a 4-year and 10-month-old girl who presented with clinical evidence of MG before thoracotomy and who developed florid MG after thoracotomy for removal of an anterior mediastinal mass later documented to be a thymoma.

Cardiac tamponade caused by a mediastinal teratoma

Mediastinal masses in children younger than 2 years often cause symptoms from tracheal compression, but clinical indications later in childhood are less frequent. Mediastinal teratomata arise in the anterior region, and when they produce symptoms these are usually manifestations of tracheal compression, pain, pleural perforation or secondary infection of the tumour. Pericardial perforation is a rare and life-threatening complication. A case of sudden pericardial perforation and cardiac tamponade caused by a mediastinal teratoma is described.

An unusual cause of neonatal respiratory distress. RDS in a neonate with a neuro-enteric cyst

A 2.5 kg male infant developed respiratory distress in the neonatal period. A diagnosis of idiopathic hyaline membrane disease was made and he was treated accordingly. At 24 hours of age he required intubation, and the immediate and dramatic improvement in his condition suggested that the original diagnosis was incorrect. Closer examination of the chest X-ray revealed an intrathoracic cyst and abnormal vertebrae. The cyst was removed surgically, and histological examination showed it to be a neuro-endodermal cyst.

Adenocarcinoma arising in an intrathoracic duplication cyst of foregut origin: a case report with review of the literature

A 41-year-old man presented with an asymptomatic superior mediastinal mass. At thoracotomy, a duplication cyst of the foregut was found. Microscopic examination of the cyst revealed mucosal alterations ranging from dysplasia and in situ carcinoma to infiltrating colonic carcinoma. Although malignant change has been reported in intra-abdominal foregut cysts, this is the first reported instance of carcinoma arising in a mediastinal duplication cyst.

Intrathoracic neural tumours

The experience of one regional thoracic surgical unit in managing intrathoracic neural tumours over a 25-year period is presented. Neural tumour was diagnosed in 55 patients, of whom 41 were asymptomatic. In 11 patients complete resection was not achieved--the reasons for this and its effect on the outcome of the patient are discussed. There were 52 posterior mediastinal and three lateral chest wall tumours. The pathological distribution was as follows--benign nerve sheath tumours (neurofibroma, neurilemoma) 39, ganglioneuroma 13, and neuroblastoma 3. One neurofibroma recurred as a neurosarcoma six years after its apparently complete resection and was removed by an extensive resection at reoperation. One neuroblastoma recurred within the spinal canal four years after incomplete excision at thoracotomy--this patient died subsequently of widespread metastatic neuroblastoma. No other tumour is known to have recurred.

Thoracic neurolophomas

Neural crest cells are unique. Few tissues found in the embryo are expressed with such diversity in adults. Cellular differentiation occurs simultaneously with widespread migration. Neural crest cell neoplasia results in some of the most common tumors clinically encountered. As a group, these tumors are called neurolophomas. This report describes the neural crest formation, the tissues normally derived from it, a classification of the neural crest tumors, and a review of such tumors as they arise in the thorax.

Intrapericardial bronchogenic cysts

A rare case of large intrapericardial bronchogenic cyst with superior vena caval obstruction is reported. The cyst was successfully removed and the superior vena cava, which was narrowed by pressure fibrosis and thrombosis, was reconstructed satisfactorily and has maintained patency. In another case a large cyst of the same type without vena caval obstruction was successfully treated surgically. The features of these 2 cases are compared with those of 20 reported cases. The angiographic data in these cases appear to be sufficiently characteristic to suggest the nature of the lesion and the clinical finding of pericarditis early in the course of the disease may also suggest the diagnosis.

Leiomyosarcoma of the mediastinum

A case of leiomyosarcoma of the posterior mediastinum is presented; 2 other malignant and 7 benign smooth muscle tumours of the mediastinum have been collected from the literautre. The tendency for blood-borne and local recurrence in the leiomyosarcomas is demonstrated. Various theories for the origin of these tumours are examined.

Cystic intrathoracic derivatives of the foregut and their complications

It is suggested that these lesions should be classified into three main categories based on embryology—bronchogenic cyst (resulting from a defect of lung budding), intramural oesophageal cyst (true duplication), and enteric cyst (resulting from the split notochord syndrome). A series of 41 patients is reported. Seven of our patients suffered complications, and in two cases these nearly resulted in the death of the patient. These complications are described and their serious import is used to emphasize the desirability of surgical removal of all these foregut derivatives before complications ensue.

Thoracic enteric cysts and diverticulae

Six cases of thoracic enteric cysts and diverticulae are described to illustrate a manifestation of the split notochord syndrome. The varied clinical, radiological, and operative picture in these cases is emphasized, the common triad being respiratory symptoms, a posterior mediastinal mass, and a vertebral anomaly. The symptoms may, however, be entirely gastrointestinal in the form of abdominal enlargement or gastro-intestinal haemorrhage. Because of the diversity of presentation these patients may come under the domain of the paediatric surgeon, the thoracic surgeon, or the neurosurgeon, and occasionally a combined team approach may be required to obtain satisfactory results in surgical treatment, which is mandatory.

Complications of mediastinal neural tumours

Thirty-two mediastinal neural tumours were seen in the East Anglian Regional Thoracic Surgical Unit at Cambridge between October 1952 and July 1970. The descending order of frequency was neurofibroma, ganglioneuroma, neurilemmoma, neurofibrosarcoma, and neuroblastoma. The literature relating to these tumours is reviewed and the pathological and clinical complications encountered in this series and in the literature are described.

Endobronchial teratoma associated with bronchiectasis and bronchiolectasis

A teratoma in a young West Indian of Negro race is reported. The teratoma presented radiologically in the left upper lobe as an ill-defined shadow which contained a crescent-shaped translucent area and simulated a mycetoma. In addition, the left lung showed widespread nodular shadows. The left lung was resected and the teratoma was found to be endobronchial in position. This is a very rare site for a teratoma as only one of the 15 previously reported intrapulmonary teratomata may have been endobronchial. The remainder of the left lung remote from the tumour showed generalized bronchiectasis both radiologically and pathologically. The bronchiectasis was of follicular type and in addition there was widespread bronchiolectasis. The inflammatory reaction associated with the latter was responsible for the nodular shadows. The significance of these changes in relation to the teratoma is discussed.

Cystic thymomas and thymic cysts. A review

Six cases of large thymic cyst are described; five were cystic thymomas and one was nonneoplastic. Two of the thymomas were not only grossly degenerate but showed severe chronic inflammatory change, so that the diagnosis might be missed. The classification of cysts into congenital, inflammatory, and neoplastic groups is discussed. Cystic teratomata of the thymus, lymphatic cysts, and bronchogenic cysts are classed separately since thymic location does not affect their natural history. Cystic thymomas are still not well known clinically, and the literature on the subject is reviewed. It is probable that quite a few non-specific cysts of the anterior mediastinum are of thymic origin.

Mediastinal duplication of the gut

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