Ann Thorac Surg 2008;86:302-304. doi:10.1016/j.athoracsur.2007.07.087
© 2008 The Society of Thoracic Surgeons
Case Reports
An Unusual Case of Giant Mediastinal Teratoma With Malignant Transformation
Chang Chen, MDa,*,
Hui Zheng, MDb,
Sen Jiang, MDc
a Department of General Thoracic Surgery, Tongji University-Affiliated Shanghai Pulmonary Hospital, Shanghai, China
b Department of Pathology, Tongji University-Affiliated Shanghai Pulmonary Hospital, Shanghai, China
c Department of Radiology, Tongji University-Affiliated Shanghai Pulmonary Hospital, Shanghai, China
Accepted for publication July 27, 2007.
* Address correspondence to Dr Chen, Zhengmin RD 507, Shanghai, 200433, China (Email: chenchang{at}nju.org.cn).
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Abstract
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Mediastinal teratoma with malignant transformation is extremely rare. It consists of two components: (1) a pre-existing mature teratoma and (2) a nongerm cell malignant tumor. The radiologic appearances are usually straightforward, including a cystic mass and findings suggestive of malignancy. The authors describe an unusual case of giant mediastinal teratoma with malignant transformation in a 59-year-old patient. Radiographically, multiple spherical nodules appeared in the cyst that necessitated differentiation from hydatid disease. Computed tomography, magnetic resonance imaging, and operative and pathologic findings are provided.
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Introduction
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Giant mediastinal teratoma with malignant transformation (TMT) has been extremely rare [1–3]. Histologic evidence of two components is mandatory for diagnosing TMT: (1) a pre-existing mature teratoma and (2) a nongerm cell malignant tumor. Classic radiologic appearance of a cystic mediastinal teratoma is a lobulated, usually thin-walled, inhomogeneous cystic mass in the anterior mediastinum. Several tissue types may appear at different densities. When considering malignant transformation, a locally thickened and solid wall with invasion of adjacent structures would be most likely [1]. All of these radiographic characteristics are considered significantly distinct from echinococcosis pulmonum. However, in the following case of a TMT, the radiographic appearance of multiple spherical mini-nodules in a giant cyst necessitated differentiation from hydatid disease. We believe that such appearances have not been previously reported.
The patient, a thin, 59-year-old woman, initially presented with chest distress, dyspnea, and a frequent dry cough for the prior month. Her past medical and surgical history was unremarkable. No history of animal contact was available. On physical examination she was afebrile with stable vital signs. Extremely weak breath sounds and dullness to percussion were heard in her left chest. No rales, rhonchi, or significant wheezing were heard. Her right cardiac margin was shifted 6 cm to the right.
Further workup showed a normal complete blood count and chemistry lab values. Arterial blood gas analysis suggested hypoxemia; PO2 was 70 mm Hg, SO2 95%. Serum carcino-embryonic antigen, neurone specific enolase, and β-human chorionic gonadotropin levels were within normal range; alpha-fetoprotein and CA242 levels were elevated to 19.0 ng/mL (normal, 0 to 15) and 495.6 U/mL (normal, <25l), respectively. Pulmonary function tests showed a forced expiratory volume in 1 second of 0.62 L, 27.9% of prediction, and forced vital capacity of 0.92 L (34.1%). 99mTc-macroaggregated albumin radionuclide imaging confirmed approximately 10% perfusion and ventilation on the left and 90% on the right.
Her posteroanterior and lateral chest x-ray films showed a giant mass occupying the majority of the left chest, with evidence of tracheal displacement and deviation of the cardiac shadow to the right. A helical computed tomographic scan (Fig 1a) demonstrated a large cyst with sharp margins. The adjacent lung was compressed and the mediastinum was pushed to the contralateral side. No vessel invasions or entanglement were demonstrated. Unusually, there were multiple small balloon-like inclusions (in diameters approximating 1 to 1.5 cm) scattered throughout the cyst. The spherules were of lower density than the surrounding fluid; therefore, they seemed to be assembled mostly in the uppermost part of the cyst while the patient was in a supine position. Thoracic effusion was notable. Under magnetic resonance imaging examination (Fig 1b), these daughter spherules showed medium signal intensity both on T1-weighted and T2-weighted images. The background cystic fluid exhibited a high-intensity signal on T1-weighted images, suggesting sebaceous component. From a radiologic view, the cyst was more likely a giant teratoma, whereas mediastinal parasitosis was the other differential.
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Fig 1. Radiographic images of the giant mediastinal cyst. (a) Helical computed tomographic scan demonstrates a large cyst with sharp margins and multiple spherules found mostly in the upper region. (b) T2-weighted magnetic resonance image shows the majority of left chest cavity occupied and mediastinum shift contralaterally by the mass. Spherules exhibit medium signal intensity.
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Examination of pleural effusion was not diagnostic. Bronchoscopy showed a nearly occluded left main bronchus due to compression that resulted in difficult bronchoscope insertion. Endobronchial mucosa was otherwise normal; therefore, the biopsy was not performed. A Casoni's intradermal test was negative.
The patient underwent subsequent thoracotomy for further biopsy and resection. The cystic tumor had a comparatively thick wall (located in the left lower mediastinum) with a diameter of 18 cm. There was obvious adherence to the adjacent hilar structures and diaphragm, but no erosion was noted. Except for the intense adhesions and a large thoracotomy, the tumor was removed without much difficulty. On specimen examination the tumor contained mostly a green-yellowish fluidic material and multiple cheese-like spherules, which were 1 to 1.5 cm in diameter and were easily crushed when touched with scissors (Fig 2). However, no parasite-containing cysts were found. Unexpectedly, cut sections showed that the inferior wall of the tumor was significantly thickened and consolidated with an uneven surface. In addition, several tiny nodules were noticed on the visceral pleura and diaphragm. Frozen section confirmed adenocarcinoma of the solid wall and nodular pleural metastasis, albeit a benign nature of the tumor. Further extrapleural pneumonectomy was considered a possible cure, but the patient declined due to the increased risk of postoperative respiratory failure considering her poor lung function test results.
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Fig 2. Gross appearance of the mass and spherules (cheese-like spherules, 1 to 1.5 cm in diameter and easily fragmented).
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Microscopy showed that the cystic mass was lined by skin, adnexa and columnar epithelium, and cartilaginous islands. The spherules were composed of noncellular frameless sebaceous-containing material. Final histologic diagnosis was a giant mature mediastinal teratoma with local adenocarcinoma transformation and pleural metastasis. The patient recovered uneventfully and was discharged home on postoperative day 7. Unfortunately, she died in a traffic accident after two cycles of postoperative chemotherapy.
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Comment
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At radiography, cystic mediastinal teratomas are typically described as encapsulated, well-marginated, spherical, or lobulated masses that contain heterogeneous tissue types, such as soft tissue, calcium, fluid, and fat [4]. Fluid and fat are the most prominent components in cystic teratomas with 76% having low radiolucency, which is representative of fat, and 2% may have a fat-fluid level, which is highly specific [5]. On magnetic resonance imaging the sebaceous component of the mass shows high-signal intensity on T1-weighted images and variable signal intensity on T2-weighted images. Homogeneous internal density is found in 10% of cystic teratomas [6], exhibiting as a unilobular cystic mass with volume-occupying effect.
The unique characteristics in our case were the floating multiple round spherules in the giant cyst, which called for a differential diagnosis from echinococcosis pulmonum. A typical hydatid cyst often occurs as an intrapulmonary mass and its incidence at the mediastinum is lower than 1.2% [7]. We believe that no more than five cases of hydatid disease involving the thymus have been previously described. In the present case, the lack of animal contact as well as a negative Casoni's intradermal test decreased the likelihood of hydatid disease. Although magnetic resonance imaging examination helped to define the daughter parasitic cysts based on signal intensity scales, appearance of these small intracystic spherules was still confusing. Second, malignant transformation in a giant mediastinal teratoma is uncommon. These nongerm cell malignancies are postulated to originate either from totipotential germ cells differentiation to a somatic type or from pre-existing mature teratoma elements to nongerm cell malignancy. Teratomas with malignant transformations often have certain radiographic characteristics when they contain carcinomatous contents. These teratomas can demonstrate fatless solids [5] or show a thick contrast-enhancing capsule with a rough and uneven internal surface. Invasion into surrounding structures may also been seen [1]. Such changes were minor to note in our case, most likely due to the inferior location and close relationship to the diaphragm.
Prognosis of TMT is generally poor [8]. A high frequency of metastases, as well as rapid disease progression and high recurrence rate, is associated with its aggressive behavior. In Mesbahi and colleagues' [9] series, 3 patients with mediastinal TMT were noted to have only 4 to 6 months of treatment response, despite comprehensive treatment of surgery, chemotherapy, or radiation [9]. Pleural dissemination of the carcinomatous component, as described in our case, demonstrates again that TMT may have early local spread. Prognosis of TMT depends mostly on disease stage and treatment modality. Surgical resection plays an essential role in therapy when the tumor is limited to a single site, but the role of chemotherapy has not been adequately addressed. Adapted chemotherapy based on histology (such as fluorouracil-based regime for adenocarcinoma transformation) has recently been advocated by Mesbahi and colleagues' [9] and Donadio and colleagues' [10], and it may help improve patient outcome.
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References
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Abstract
Introduction
