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New Haven, CT
Dr. Ponn is Associate Chief of Surgery at Yale New Haven Hospital.
Correspondence to: Ronald B. Ponn, MD, FCCP, Yale New Haven Hospital, 330 Orchard St, Suite 300, New Haven, CT 06511; e-mail: rbponn{at}aol.com
I recall the first case that I "scrubbed on" as an eager medical student in 1973 at a Boston teaching hospital was that of a man of about 70 years who presented with a cough. Then, patients were hospitalized for "workup" and "buffing up" in advance of the operation. The medical student was first to interact with the patient: take the history and perform the physical examination, type or write the findings on the chart, order tests that the residents wanted, and report the results on morning rounds (very early morning rounds; 5:30 AM, to be exact). In this case, the chest radiograph showed a left mid-lung field opacity. Linear tomograms may have been performed, but CT scanning was not available. Because of the possibility of cancer, the patient underwent a full posterolateral thoracotomy and was found to have a pseudotumor (ie, fluid in the interlobar fissure). The surgical team was pleased that there was no cancer and related the good news to the patient, who also was pleased, and he was discharged from the hospital about 10 days later. The surgeons acted in the best interests of the patient based on the information available. I do not know whether his cough was relieved by surgical intervention, but I suspect not.
Fortunately, much has changed. Thoracotomy for benign lesions, which accounted for 
60% of operations in the 1960s and 1970s, especially in endemic fungal regions, is now rare. In addition, nonresective thoracotomy for lung cancer currently occurs in < 5% of cases. There are two reasons for this improvement. First and foremost are the dramatic advances in imaging that have occurred in the last 2 decades and that continue to evolve exponentially. Second, procedures such as needle biopsy and thoracoscopy have markedly reduced the need for thoracotomy. Although still occasionally required and associated with low risk, open surgery, including minimal thoracotomy, that yields a benign diagnosis invariably induces this thoracic surgeon to retrace the pathway that led to the operating room to determine whether other options might have been preferable. What these musings have to do with mediastinal cysts is that, like the pseudotumor, these cysts are benign, can be diagnosed with certainty by imaging, and are mostly asymptomatic. If doubt remains or if symptoms are thought to be related to the cyst, procedures other than open operation, some nonsurgical, may be applicable.
In this issue of CHEST (see page 125) Takeda and associates report on a half-century institutional experience with mediastinal cysts. Unfortunately, the present report suffers from the problems of most discussions of this subject. The literature consists of small series. Conclusions are further confounded by the inclusion in most reports of only surgical cases and, perhaps in order to achieve a presentable number of patients, combine cysts of various etiologies. In addition, symptomatic cysts in infants and children are clinically different from those discovered incidentally in adults. The present report includes 10 pediatric cases. As the authors note, the compression of pliable adjacent structures is more common in children, and therefore cysts are more likely to be symptomatic and more clearly related to symptoms in this group. Severe, or occasionally life-threatening, problems are more likely in children. The inclusion of pediatric cases in the "spectrum" of mediastinal cysts is a weakness of this and other reports. It is to the authors’ credit, however, that they eliminated parenchymal cysts from this series, although the discussion refers to complications from these cysts and is thus somewhat confusing.
My major criticism is that the authors reassert the traditional dogma that mediastinal cysts, even if asymptomatic, should be treated surgically. They further state that such treatment needs to be "immediate." The basis for their approach appears to be fourfold. The first argument is histologic; that is, cysts may harbor cancer, and a definitive diagnosis can be made only by resection. Second, cysts are likely to cause problems in the future even though they may be quiescent at presentation. Third, surgery relieves symptoms. Fourth, surgical treatment is associated with minimal morbidity.
Despite a few case reports, the incidence of malignancy in simple cysts is vanishingly low. Although the authors refer to malignancy associated with bronchogenic cysts as an "important issue," no cancers were found in their series. In a comprehensive review, Marchevsky and Kaneko1 noted that "malignant transformation of the epithelial components of a bronchogenic cyst has not been described." Bolton and Shahian2 also have questioned whether reports of malignant transformation in adults are reliable. The fear of cancer is not an indication for the resection of simple mediastinal cysts any more than for asymptomatic epiphrenic, Zenker, or duodenal diverticula, despite a handful of reports of associated cancers. Perhaps, a positron emission tomography scan following the identification of a mediastinal cyst may be helpful in this regard. The second histologic argument for routine resection is that this is the only way to establish a firm diagnosis. Again, the authors’ own experience weakens this point. Modern imaging, mainly CT scanning and sometimes MRI, can accurately demonstrate a true simple cyst (ie, a smooth-walled mass with contents of water density or thicker but homogeneous mucinous material).
The assertion that asymptomatic cysts will ultimately cause problems has not been proven. St.-Georges and associates3 noted eventual symptoms in 90% of patients with parenchymal bronchogenic cysts, but in only a third of those with mediastinal bronchogenic cysts. Again, this was a surgical series and was limited to bronchogenic cysts. In fact, the natural history of mediastinal cysts that are asymptomatic at presentation is unknown. In the present report, the two patients who refused surgery did not develop problems from their cysts. In the series of Ribet and colleagues,4 5 of 69 patients declined surgery, but follow-up was available in only two patients, neither of whom developed problems. Catastrophic outcomes in adults with simple cysts are exceedingly rare, are nonlethal if managed appropriately, and therefore do not warrant universal resection. Since mediastinal bronchogenic cysts and esophageal cysts, as opposed to parenchymal cysts, rarely communicate with the airways or the esophagus, there is no inherent reason why one should assume that they will inevitably enlarge, rupture, become infected, or otherwise lead to clinical problems.
All series report a certain percentage of patients who present with symptoms that lead to imaging that identifies the cyst. With the exception of cysts that cause the compression of vital structures, are infected, or are of sufficient size to result in the patient sensing "something" in the chest, the relationship of cysts to symptoms is unclear. Although chest pain or cough is frequently cited as a presenting symptom, the reason why a small cyst should cause symptoms is often elusive. Likewise, this and other series rarely confirm whether the symptoms are relieved following an operation. While bronchogenic and esophageal duplication cysts may be symptomatic because of their location, I have generally found it difficult to relate most pericardial and pleural mesothelial cysts to patient complaints. The issue of dysrrhythmias associated with pericardial cysts is another unknown. I believe that most are found incidentally. Logically, why should a simple pericardial cyst cause cardiac problems?
About a third of the adult patients in the present report had thymic cysts. As noted by Shields,5 the presence of a thymoma in a simple unilocular thymic cyst is rare. The radiographic features of cystic thymoma or multilocular thymic cysts are vastly different from those of simple cysts. Finally, two meningoceles are included in the study, both occurring in patients with neurofibromatosis. Although there is risk of cord herniation in this setting, the risk is very low and usually can be predicted by imaging. In addition, these defects are often multiple and bilateral, again complicating the case for surgery as a universal treatment.
The authors report that "there was no major morbidity or mortality in the surgical treatment of mediastinal cysts." While mortality is clear, the term major morbidity is undefined. They note that 19 of the most recent 28 patients were treated by thoracoscopic operations (ie, video-assisted thoracoscopic surgery [VATS]). This is to their credit. Certainly, most mesothelial and thymic cysts can be handled by VATS. Bronchogenic cysts, which are the most likely cysts to require treatment for symptoms, in contrast, are often associated with a fibrotic reaction that makes VATS dissection difficult. Martinod and associates,6 for example, had to convert to thoracotomy in 7 of 20 such cases that were initially approached by VATS, two because of significant bleeding. The mean hospital length of stay in this report was 5 days for the VATS group and 8.5 days for the open surgery group. Of the 20 patients reported on by Zambudio and colleagues,7 5 had complications, one of which was phrenic nerve paralysis after the resection of a mesothelial cyst.
In summary, the belief that all mediastinal cysts in adults should be treated surgically requires reconsideration. Malignancy is not an issue. The cyst is often not related to the presentation. Modern imaging is highly accurate in delineating simple cysts. Resection is not without hazard. For classic simple cysts, unlike some indeterminate pulmonary nodules, for example, follow-up in many cases need not be frequent or expensive. The use of words such as tumor, the possibility of missing cancer, the fear of future catastrophe, and claims that an operation is always innocuous and is the only option appear to me to cloud a rational approach to mediastinal cysts. Nonetheless, any mediastinal cyst that is not classically "simple" or is one that is clearly causing symptoms warrants intervention. In many cases, percutaneous aspiration or mediastinoscopy may obviate the need for thoracotomy or VATS.8 9 10
References
This article has been cited by other articles:
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  D. Pop, N. Venissac, F. Leo, and J. Mouroux Video-assisted mediastinoscopy: A useful technique for paratracheal mesothelial cysts J. Thorac. Cardiovasc. Surg., March 1, 2005; 129(3): 690 - 691. [Full Text] [PDF]
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 M. A. Savitt, G. Gao, A. P. Furnary, J. Swanson, H. L. Gately, and J. R. Handy Application of Robotic-Assisted Techniques to the Surgical Evaluation and Treatment of the Anterior Mediastinum Ann. Thorac. Surg., February 1, 2005; 79(2): 450 - 455. [Abstract] [Full Text] [PDF]
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T. Weber, T. C. Roth, M. Beshay, P. Herrmann, R. Stein, and R. A. Schmid Video-assisted thoracoscopic surgery of mediastinal bronchogenic cysts in adults: A single-center experience Ann. Thorac. Surg., September 1, 2004; 78(3): 987 - 991. [Abstract] [Full Text] [PDF]
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