Ann Thorac Surg 2009;87:1274-1275. doi:10.1016/j.athoracsur.2008.08.011
© 2009 The Society of Thoracic Surgeons
Case Reports
Malignant Invasive Thymoma in the Posterior Mediastinum
Alpay Orki, MDa,*,
Mehmet Suat Patlakoglu, MDb,
Canan Tahaoglu, MDc,
Cemal Asim Kutlu, MD, FETCSb
a Department of Thoracic Surgery, Maltepe University, Süreyyapa
;a Chest Diseases and Thoracic Surgery Training Hospital, Istanbul, Turkey
b Department of Thoracic Surgery, Süreyyapaa Chest Diseases and Thoracic Surgery Training Hospital, Istanbul, Turkey
c Department of Pathology, Süreyyapaa Chest Diseases and Thoracic Surgery Training Hospital, Istanbul, Turkey
Accepted for publication August 6, 2008.
* Address correspondence to Dr Orki, NATO Yolu, Bosna Bulvari, 
zmir Sokak, Camlica Plamiye Sitesi 11-3, Yavuzturk-Uskudar-Istanbul, 34692, Turkey (Email: alpayorki{at}yahoo.com).
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Abstract
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We present a rare case of malignant invasive thymoma (type A) arising from the posterior mediastinum. A 17-year-old girl was referred to our clinic after detection of a mass on a chest roentgenogram. Thoracoscopy showed a lobulated, pale yellowish mass located in the posterior compartment together with several foci in the lung parenchyma. The tumor and parenchymal foci were totally resected through a left minithoracotomy. Postoperative pathology revealed malignant invasive thymoma type A.
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Introduction
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Thymomas are the most common primary tumors originating from the anterior mediastinum. However, they may arise from other compartments of the mediastinum, thoracic cavity, lung parenchyma, and even from the neck [1]. Resection is usually indicated not only for diagnosis but also for staging. The completeness of resection is the most important factor affecting survival [2]. This article presents the case of a young woman who underwent left thoracotomy for a mass in the posterior mediastinum, and for whom postoperative histology revealed malignant invasive thymoma type A.
A 17-year-old girl was referred to our department after a mass was detected on a chest roentgenogram. Apart from left back pain and coughs lasting for 2 months, her medical history was uneventful. Findings from the physical examination and laboratory workup were within normal limits. Chest roentgenogram and contrast-enhanced computed tomography (CT) displayed a mass in the left chest without an invasion of the chest wall or mediastinal structures. No peripheral lymphadenopathy was detected by physical examination. Thorax CT and magnetic resonance imaging did not demonstrate a lesion in thoracal wall, mediastinal compartments or in the lungs except the tumor localized to posterior mediastinum (Fig 1).
Video-assisted thoracic surgery (VATS) was planned without further investigation. Bronchoscopy, which revealed no endobronchial lesion, was performed before the procedure. A lobulated, pale yellowish mass sized 4 x 6 cm was observed arising from the posterior mediastinum along with several foci—the largest of which was 4 mm in diameter—in the neighboring parenchyma. The procedure was converted to minithoracotomy for a proper examination of tumor dissemination. No lesion was determined in chest wall or mediastinal fat pad. No lymph node of pathologic size or form was observed. The tumor was completely resected, and wedge resection was performed for the parenchymal lesions.
The patient's postoperative course was uneventful. Her chest tube was removed on postoperative day 1, and she was discharged from the hospital on day 3.
Microscopic examination revealed predominantly spindle-shaped epithelial cells that were arranged in a fascicular, storiform, or peristomatous pattern. The spindle-shaped cells were elongated, possessing bland-looking nuclei with fairly dense chromatin and indistinct nucleoli. Mitotic figures were absent or very sparse (Fig 2). Gland or microcyst formation was common. The final pathology evaluation showed that the mass and parenchymal foci were both malignant invasive thymoma type A. According to the Masaoka staging system, the tumor was stage IVa.
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Fig 2. Histologic section of tumor shows predominantly spindle-shaped epithelial cells arranged in a fascicular, storiform, or peristomatous pattern (hematoxylin and eosin stain, original magnification x100).
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The patient was postoperatively evaluated by the council of surgery, which consisted of surgeons, chest physicians, a pathologist, a medical oncologist, and a radiologist. Administration of adjuvant chemoradiotherapy (chemotherapy with cisplatin, 3 cycles, plus radiotherapy, 50 Gy) was decided because the clinical behavior of ectopic thymomas is unpredictable. A surgical specimen was reviewed by a senior pathologist (I. O.) to confirm the diagnosis. The patient was consequently referred to the oncology department for adjuvant therapy.
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Comment
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A three-compartment model comprising an anterior-superior compartment, a visceral (middle) compartment, and the bilateral paravertebral sulci (posterior) is the most accurate anatomic representation of the mediastinum. Thymic lesions are most frequently observed in the anterior compartment [3]. Only 4% of thymomas are detected in the other compartments of the mediastinum and neck [4]. Embryologically, thymic epithelium arises bilaterally from the third and probably the fourth bronchial pouches and migrates into the anterior-superior mediastinum. Ectopic thymomas are considered to arise from distributed thymic tissues that fail to migrate into the anterior-superior mediastinum [3].
It is widely accepted that surgical resection is the mainstay of tumor management. In the reported series, survival rates reach 100% in patients who receive complete resection for stage 1 disease [1, 4]. Even in advanced-stage thymomas (Masaoka III to IV), the 5-year survival is reported to be approximately 43% [2]. In patients in whom complete resection cannot be accomplished, subtotal resection is reported to provide better survival rates than simple biopsy in advanced tumors. Therefore, patients who present with a mediastinal lesion suggesting thymoma are considered to be candidates for tumor excision without further investigation. Any attempt at tissue diagnosis unavoidably results in capsular damage and the subsequent implantation of tumor cells into the chest wall or pleural space [2, 5].
Although stage-based therapy of mediastinal thymomas is controversial, developing a therapeutic protocol is easier because the behavior of the tumor is well known. However, experience with ectopic thymomas is insufficient to provide detailed information on clinical progress and survival. Therefore, in accordance with our routine policy for stage IVa thymomas, the current patient was referred to the oncology department for adjuvant therapy. Clinical follow-up with roentgenogram, CT, positron emission tomography-CT, and magnetic resonance imaging was preferred for the remaining thymus rather than surgical resection. Although the patient is still undergoing routine clinical follow-up, she remains free of recurrent disease.
In conclusion, thymomas must be considered in the differential diagnosis of visceral and posterior mediastinal tumors. If radiology suggests that the tumor can be totally removed, no further tissue diagnosis is warranted. Surgeons should not hesitate to convert to open thoracotomy when there is any suspicion of the necessity for complete resection.
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Acknowledgments
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We wish to thank senior pathologist Professor Ibrahim Oztek, MD.
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References
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- Kojima K, Yokoi K, Matsuguma H, et al. Middle mediastinal thymoma J Thorac Cardiovasc Surg 2002;124:639-640.[Free Full Text]
- Deterbeck FC, Parsons AM. Thymic tumors Ann Thorac Surg 2004;77:1860-1869.[Abstract/Free Full Text]
- Kanzaki M, Oyama K, keda T, Yoshida T, Murasugi M, Onuki T. Noninvasive thymoma in the middle mediastinum Ann Thorac Surg 2004;77:2209-2210.[Abstract/Free Full Text]
- Yamazaki K, Yoshino I, Oba T, et al. Ectopic pleural thymoma presenting as a giant mass in the thoracic cavity Ann Thorac Surg 2007;83:315-317.[Abstract/Free Full Text]
- Matsumoto K, Ashizawa K, Tagawa T, Nagayasu T. Chest wall implantation of thymic cancer after computed tomography-guided core needle biopsy Eur J Cardiothorac Surg 2007;32:171-173.[Abstract/Free Full Text]
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Abstract
Introduction
