British Journal of Radiology 74 (2001),1148-1149 © 2001 The British Institute of Radiology
Ruptured mediastinal cystic teratoma with intrapulmonary bronchial invasion: CT demonstration
Y-C Cheung, MD
1,2
S-H Ng, MD
1,2
Y-L Wan, MD
1,2 and
K-T Pan, MD
1
1Department of Diagnostic Radiology, Chang Gung Memorial Hospital at Linkuo and Keelung, 5 Fu-Hsing Road, Tao Yuan Hsien and 2College of Medicine and School of Medical Technology, Chang Gung University, 259 Wen Hwa 1st Road, Kwei Shan, Tao Yuan Hsien, Taiwan
Correspondence: Dr Y-C Cheung, Department of Diagnostic Radiology, Chang Gung Memorial Hospital, 5 Fu-Hsing Road, Kwei Shan, Tao Yuan Hsien, Taiwan
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Abstract
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Ruptured cystic mediastinal teratoma is rare. The diagnosis of this condition and a clear demonstration of its associated complications are important for defining the surgical approach. We report the CT findings of a case of mediastinal cystic teratoma before and after rupture. CT features of bursting of the spherical fatty compound and intrapulmonary bronchial invasion have not been previously described.
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Introduction
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Cystic teratoma is the most common primary germ cell tumour in the mediastinum [1]. It is composed of ectodermal, mesodermal and endodermal derivatives. Typical CT appearances are an encapsulated mass with a smooth wall containing soft tissue, fluid, fat, calcification or any combination of these [2, 3]. On rare occasions, cystic teratomas rupture into adjacent structures such as the pleural space, pericardium, lung or tracheobronchial tree [4]. We present a case of a cystic teratoma that ruptured in the mediastinum with involvement of the intrapulmonary bronchus, resulting in obstructive pneumonitis. To our knowledge, these radiological appearances have not been previously reported.
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Case report
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A 25-year-old female was admitted to hospital because of recurrent haemoptysis and chest pain for 2 months. She also complained of mild dyspnoea on exertion. 2 years previously she was incidentally found to have a mediastinal mass with CT features of teratoma, but she refused surgical treatment. On admission, physical examination showed decreased breath sounds in the medial aspect of the left upper chest. The laboratory data were unremarkable. Bronchoscopy showed occlusion of the left upper bronchus with intermittent oozing of fresh blood. She denied any traumatic history during the onset of symptoms.
Chest radiography showed widening of the mediastinum, with an irregular mass in the left upper perihilar region. Consolidation of the left upper lobe was also noted. Review of CT from 2 years previous showed a 3 x 4 cm2 mass in the anterior mediastinum, composed of a large cystic space and small discrete areas of soft tissue and a spherical fatty component. The mass had a smooth margin with a thin wall (Figure 1
). All these CT features were consistent with a mature cystic teratoma. On CT during the present admission, the tumour had enlarged to 4 x 6 cm2 and its margin had become poorly demarcated. The internal architecture of the mass was now strikingly inhomogeneous, with mixed cystic and solid areas. The spherical fat component had changed to several fatty fragments, and the mediastinal fat was noted to have a "dirty" appearance. The tumour extended to the adjacent lung and encased the left upper lobe bronchus, contributing to left upper lobe consolidation (Figure 2). No pleural or pericardial effusion was present. Rupture of the mediastinal cystic teratoma with intrapulmonary bronchial invasion was diagnosed. Lobectomy and excision of anterior mediastinal tumour were then performed. A large irregular mass, tightly adherent to the lung and pericardium, was resected. The tumour contained yellowish sebaceous material as well as some hair and fat. Microscopy showed cystic lesions lined by skin, adnexa and columnar epithelium, pancreatic tissue and cartilagenous islands. Tumour extension into the bronchial tree and distal obstructive pneumonia were found. There was no tumour component within the consolidated lung. Ruptured cystic teratoma was confirmed, and no immature component or malignancy was identified. The patient remains well after surgery.
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Figure 1. Non-enhanced CT, 2 years prior to hospital admission, shows a 3 x 4 cm2 encapsulated tumour in the anterior mediastinum containing a cystic configuration, soft tissue and a spherical fatty component. The tumour margin is smooth. These CT features are diagnostic of cystic teratoma.
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Figure 2. Contrast enhanced CT at the time of admission shows a 4 x 6 cm2 heterogeneously enhanced mass with disorganized cystic and soft tissue components. Fat fragments are dispersed within the tumour (arrowhead). Note the direct invasion to the intrapulmonary left upper lobe bronchus (arrow).
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Discussion
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Mediastinal teratomas are asymptomatic in up to 53% of cases and are frequently discovered incidentally on chest radiography performed for other reasons [5]. Occasionally, the mass effect on adjacent structures or the functional activity of dermal derivatives may cause signs and symptoms. Rupture of a mediastinal cystic teratoma is rare but is always symptomatic. Common clinical symptoms following rupture are haemoptysis and chest pain, which occasionally progress to acute respiratory disease [6]. Prompt treatment of the ruptured tumours is essential because of progressive development of acute respiratory distress. The aetiology of rupture of mediastinal teratomas is still controversial although ischaemia, infection and inflammation have been proposed [4]. Tumour size or wall thickness are not significant predisposing factors for tumour rupture [4]. On the other hand, cystic teratomas can produce proteolytic or digestive enzymes, leading to adhesion and erosion of surrounding structures [7].
Since 90% of unruptured cystic teratomas exhibit homogeneous internal density on CT, homogeneity has been reported as the only distinguishable CT feature from a ruptured teratoma [4]. In our case, we noted the changes of a cystic mediastinal teratoma before and after rupture. CT documented the changes of the internal architecture from homogeneity to heterogeneity, the tumour margin from smooth to irregular and the fat component from spherical to a bursting configuration. Other CT findings of ruptured mediastinal teratoma, including bronchial invasion and adjacent lung consolidation, were also demonstrated. Pericardial effusion and pleural effusion have been reported in the literature as the ancillary CT findings of ruptured teratoma, but did not occur in our case. To our knowledge, the bursting sign of the spherical fatty component and intrapulmonary bronchial invasion have not been previously reported.
The demonstration of CT findings of ruptured cystic teratoma is important not only for early diagnosis, but also for surgical planning in determining the presence of tumour invasion of adjacent anatomical structures. Although atelectasis or pneumonitis account for most of the associated adjacent lung consolidation, intrapulmonary tumour infiltration is also possible. CT is the best modality to demonstrate tumour morphology and its associated complications. Although mature cystic teratoma is histopathologically benign, surgical resection is recommended owing to its potential to rupture.
Received for publication June 25, 2001.
Accepted for publication July 20, 2001.
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References
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Abstract
Introduction
