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J Thorac Cardiovasc Surg 2004;127:289-291
© 2004 The American Association for Thoracic Surgery
Brief communication |
a Department of Pathology, Nordstadt Hospital Hannover, Germany
b Department of Thoracic and Vascular Surgery, Heidehaus Hospital, Hannover, Germany
Received for publication June 7, 2003; accepted for publication July 16, 2003.
* Address for reprints: Paolo Macchiarini, MD, PhD, Department of Thoracic and Vascular Surgery, Heidehaus Hospital, Hannover Medical School, Am Leineufer 70, 30419 Hannover, Germany
pmacchiarini{at}compuserve.com
Foregut or enterogenous cysts are the result of an abnormal budding or division of the primitive foregut and are usually found in adults. On the basis of histologic features and embryogenesis, they are classified into bronchogenic, esophageal, gastroenteric, and neuroenteric cysts and usually occur in the mediastinum or, less frequently, in the soft tissues of the chest wall.1 Intrasternal foregut cysts lined by respiratory epithelium have never previously been described in the literature, and we present here the first case.
Clinical summary
A 61-year-old woman was admitted because of the onset of moderate and recurrent feeling of retrosternal pressure and pain and a cystic lesion of unknown histologic type of the manubrium sterni growing partially into the superior ventral mediastinum up to the aortic arch. Results of physical examination were normal. Conventional tomography and thoracic computed tomography (Figure 1) showed a lesion of the manubrium sterni with impression and sclerosis of the compacta. The intraosseous part of the cyst had a 1- to 2-cm wide connection to a 5 x 3-cm retrosternal extraosseous part. The extraosseous lesion was attached to the aortic arch and was limited by a calcified, enhancing capsule. Calcification of the compacta and smooth bone rimming of the perforated part of the compacta indicated the presence of a long-lasting process. Conventional radiographs of the thorax from 2 and 10 years previously also showed a cystic sternal lesion, although smaller in size. Arteriography excluded an aortic aneurysm.
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The gross examination showed that the manubrium and corpus sterni contained a unilocular cyst 5.2 cm in length with a 1.7-cm wide dorsal connection to an extraosseous tumor. The tumor appeared as a spherical bulging mass 5 cm in diameter that contained a yellow-green mucinous fluid (Figure 2). Histologically, the cyst consisted of a double layer of ciliated cuboid epithelium with an underlying thin fibrous stroma (Figure 3). Neither cartilage nor bronchial glands could be detected. Sternal cortex appeared normal. The extraosseous part of the cyst showed respiratory epithelium with more fibrous stroma. Focal regressive alterations of epithelium and stroma were noticed in the extraosseous part (metaplastic squamous epithelium, residues of hemorrhage, giant cells, proliferation of granulation tissue). Bone and periost reactions were absent. The resected thymic fat tissue was normal. The diagnosis of an intraosseous and extraosseous dysontogenetic foregut cyst was therefore made. Histochemical staining for mucopolysaccharides (periodic acid Schiff–Alcian blue stain) revealed unevenly distributed goblet cells in the parts of cyst wall lined by fully developed ciliated epithelium. Immunohistochemical staining for cytokeratins was also performed and revealed that all tested samples expressed a slightly variable degree of immunoreactivity for cytokeratins 7, 8, and 19, whereas staining for cytokeratin 20 remained uniformly negative. This staining pattern can be described as typical for ciliated respiratory epithelium, excluding any similarity to gastrointestinal tract columnar epithelium.
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Cystic structures lined by a different type of columnar epithelium originating from a different part of the primitive foregut are relatively rare anomalies. They are found in close contact with the tracheobronchial tree or the esophagus in the visceral compartment of the mediastinum.
In adults, the most common foregut cysts are the bronchogenic type, containing respiratory epithelium and cartilage or bronchial glands, and the esophageal type, containing respiratory epithelium and two or more smooth muscle layers. Because in the absence of specifically differentiated tissue other than respiratory epithelium the lesion is considered a foregut cyst,1 the cyst in our case corresponds to a foregut cyst.
During the 3rd to 4th week of gestation, the respiratory system develops from the primitive foregut as a ventral diverticulum with enlargement of two lung buds. If there is a third bud, it can separate as a foregut cyst. In the 9th week the fusion of the mesenchymal sternal bars begins. We consider that our patient's cyst originated from a supernumerary foregut bud that was included between the mesenchymal sternal bars during the 3rd through 8th weeks of gestation. The inclusion was incomplete, so that a part of the cyst wall remained extraosseous. Secretion of mucinous fluid caused an enlargement of the cyst, with secondary metaplastic squamous epithelium, hemorrhage, and fibrosis of the wall.
We only found a single case report of an intraosseous ciliated cyst, developing in the mandibular region after an autogenous bone graft from the nose to the chin when nasal respiratory epithelium was implanted traumatically into the chin.2 In our case report, the cyst was already detectable on a 10-year-old chest radiograph, and the patient's history did not include sternal injury. Teratoma, thymoma, and gastroenteric or pericardial cysts were ruled out because we found no tissue derived from more than two germ cell layers, no lymphatic tissue, no gastric or duodenal mucosa, and no flat mesothelial lining, respectively.3 As with most other visceral cystic lesions, foregut cysts must be completely resected because most will become symptomatic; complications may arise from size, fistulization, infection, and possibly even malignant alteration, and, last but not least, because operation on symptomatic cysts tends to be more complex.4 Moreover, partial excision or needle aspiration of the contents may cause recurrence.
Conclusion
We report here the first case in the literature of foregut cysts lined by respiratory-epithelium developing from a bony structure of the chest wall. This lesion was successfully managed with a partial sternectomy.
References
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