Ann Thorac Surg 2003;75:1645-1648
© 2003 The Society of Thoracic Surgeons
Case report
Malignant "triton" tumor of the posterior mediastinum: prolonged survival after staged resection
Loïc Lang-Lazdunski, MD, PhDa,*,
François Pons, MDa,
René Jancovici, MDa
a Department of Thoracic Surgery, Percy Military Hospital, Clamart, France
Accepted for publication November 13, 2002.
Keywords 13
* Address reprint requests to Dr Lang-Lazdunski, Service de Chirurgie Thoracique, Hôpital d’instruction des Armées Percy, 101 avenue Henri Barbusse, BP406, 92141 Clamart Cedex, France (Email: loic.lang{at}wanadoo.fr).
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Abstract
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Malignant "Triton" tumor is a rare subtype of malignant peripheral nerve sheath tumor showing rhabdomyoblastic differentiation. We report the case of a 22-year-old patient who had excision of such a tumor by video-assisted thoracic surgery. He was reoperated on by thoracotomy 2 months later and received adjuvant radiation, with prolonged survival. Radical surgical excision of malignant Triton tumor followed by adjuvant radiation therapy may provide the longest survival and represent the treatment of choice.
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Introduction
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Malignant tumors account for less than 1% to 2% of neurogenic tumors of the mediastinum in adults [1]. Most of those tumors occur in patients with von Recklinghausen’s disease or as a late complication of irradiation [1]. We report the case of a malignant peripheral nerve sheath tumor (MPNST) containing rhabdomyoblastic elements (malignant "Triton" tumor) occurring in a patient without von Recklinghausen’s neurofibromatosis or previous irradiation.
A 22-year-old man was referred to our Department with the presumptive diagnosis of mediastinal tumor. The patient was asymptomatic and had no cutaneous stygmates or familial history suggestive of von Recklinghausen’s disease. A routine chest roentgenogram at enrollment in the army had revealed a mass located in the right apex. Chest computed tomography (CT) and magnetic resonance imaging (MRI) showed a 5 x 2.5-cm mass located in the right paravertebral sulcus at the T2–T3 level. There was no intraspinal component, rib erosion, or invasion of surrounding organs (Fig 1). Considering location of the tumor, its probable neurogenic nature and possible malignancy, we decided to resect it.
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Fig 1. Preoperative chest magnetic resonance image (MRI). Chest MRI demonstrating a 5 x 2.5-cm rounded mass located in the right paravertebral sulcus without intraspinal component.
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The patient was operated on by videothoracoscopy on March 11, 1994. The tumor originated from the second right intercostal nerve, was adherent to the parietal pleura, and had no extension toward the spinal canal foramina. It was extracted directly through a 3-cm-access thoracotomy by enlarging the posterior port. The surgeon’s impression was that all tumor had been excised, and frozen sections revealed an apparently benign neurogenic tumor. The postoperative course was uneventful.
Pathologic evaluation of the tumor revealed a MPNST with rhabdomyoblastic differentiation (Fig 2), also known as malignant Triton tumor (MTT). Tumor cells exhibited strong immunoreactivity against anti–muscle-specific actin, anti–myoglobin, anti–neuron-specific enolase, and anti–desmin antibodies. Tumor cells exhibited intense, but focal immunoreactivity against anti–S-100 protein antibody. Tumor cells exhibited no reactivity against anti–GFAP and anti–cytokeratin antibodies. Ultrastructural study confirmed the diagnosis of MTT.
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Fig 2. Histopathology. Photomicrographs of malignant Triton tumor. Large rounded cell and intersecting spindle cells with elongated nuclei and prominent mitoses (hematoxylin–phloxine–saffron [HPS] x 200).
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Considering the high malignancy of MTT and chest wall adhesion, it was decided to reoperate on the patient, in order to achieve a more radical resection. Preoperative chest MRI disclosed a 3 x 1.5-cm mass located on the previous resection site, but it was impossible to state whether this mass was scar tissue or was a recurrence (Fig 3). The chest was entered through a right posterolateral thoracotomy in the fourth interspace, with a parascapular incision. The mass was excised en bloc together with the posterior portions of the second, third, and fourth rib and a limited wedge resection of the adjacent right upper lobe. The surgeon also excised all myocutaneous tissue around the previous access minithoracotomy. The postoperative course was complicated by a right pneumonia. Pathologic evaluation revealed no residual tumor cells in resected lung or rib tissue, but mostly scar tissue. The patient was discharged after 13 days and received adjuvant radiation therapy on the tumor site, chest wall incision, and ipsilateral superior mediastinum. Currently (May 2002), the patient is alive and disease free.
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Fig 3. Postoperative chest magnetic resonance image (MRI). Chest MRI performed 7 weeks after the first operation, demonstrating a residual mass in the right apex.
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Comment
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Masson in 1932 was the first to appreciate that rhabdomyosarcoma could develop within a peripheral nerve tumor [2]. Woodruff and colleagues in 1973 introduced the term MTT in a review of seven cases and suggested criteria for the positive diagnosis of MTT [2]. Presently, most pathologists use the term MTT for tumors, whatever their location, exhibiting the features of an MPNST and containing rhabdomyoblastic elements [3].
MTTs are extremely rare, with fewer than 100 cases reported to date [1–8]. Sixty nine percent of those tumors are diagnosed in patients with von Recklinghausen’s disease, and occur in young male patients, whereas the remaining 31% are sporadic cases mostly occurring in older women [3]. Regarding location, MTTs occur predominantly in the head, neck, and trunk regions [3]. Only six cases have been observed in the mediastinum (Table 1)
[3–8]. The natural history of MTT is much more aggressive than sporadic MPNST, and similar to high-grade sarcoma [3]. Local recurrence is common after tumor excision, whatever the location, and the 5-year survival rate has been reported to be 12% [3]. Lymphatic invasion and lymph node involvement has not been reported in patients with MTT. Recommended treatment for MTT consists of radical tumor excision with as wide a margin of normal tissue as is feasible. High-dose radiation therapy might prevent local recurrences and extend survival [3]. However, the role of adjuvant chemotherapy or radiation remains undetermined [3].
In the present case, the differential diagnosis of the tumor included schwannomas, neurofibromas, MPNSTs, nonfunctioning paragangliomas, pheochromocytomas, ganglioneuromas, ganglioneuroblastomas, Askin tumors, mesenchymomas, and granular cell tumors (Fig 3). Chest CT and MRI demonstrated no intraspinal component, no invasion of surrounding structures, and maximal diameter of 5 cm, making a VATS approach acceptable. Percutaneous transthoracic fine-needle aspiration of the tumor under either CT or ultrasound guidance was not considered because this technique is unreliable for the precise pathological diagnosis of neurogenic tumors. Only appropriate pathological evaluation can classify a neurogenic tumor as benign or malignant, and frozen sections should be used only to determinate the extent of resection (tumor-free margins). Therefore, impossibility to completely excise a tumor, or invasion of surrounding parietal or mediastinal structures, should make the surgeon convert the VATS procedure to an open procedure in order to achieve a complete excision.
It was the surgeon’s impression that all tumor had been excised by videothoracoscopy. Reoperation by thoracotomy was performed in order to achieve wider excision, as pathologic evaluation revealed an MTT, and chest MRI suggested local recurrence of the tumor. Thus, radical surgery followed by high-dose radiation therapy appeared the best option for prolonged survival and definitive cure in this young patient [3, 7].
Considering the potential for tumor implant into the chest wall after the first operation, we decided to perform radical excision of the chest wall at reoperation, followed by adjuvant radiation therapy. Considering the reports of chest wall implants after VATS excision of malignant tumors [9], we have been routinely using endobags to extract all mediastinal masses, since 1995.
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References
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- Shields TW. Benign and malignant neurogenic tumors of the mediastinum in adultsIn: Shields TW, Lo Cicero III J, Ponn PB, editors. General thoracic surgery. 5th ed. Philadelphia: Williams & Wilkins; 2000. pp. 2313-2327: Lippincott.
- Woodruff JM, Chernik NL, Smith MC, Millett WB, Foote FW. Peripheral nerve tumors with rhabdomyosarcomatous differentiation (malignant "Triton" tumors) Cancer 1973;32:426-439.[Medline]
- Brooks JS, Freeman M, Enterline HT. Malignant Triton tumor. natural history and immunohistochemistry of nine new cases with literature review. Cancer 1985;55:2543-2549.[Medline]
- Wong SY, Teh M, Tan YO, Best PV. Malignant glandular triton tumor Cancer 1991;67:1076-1083.[Medline]
- Otani Y, Morishita Y, Yoshida I, et al. A malignant Triton tumor in the anterior mediastinum requiring emergency surgery. report of a case. Surg Today 1996;26:834-836.[Medline]
- Daimaru Y, Hashimoto H, Enjoji M. Malignant Triton tumors. a clinicopathologic and immunohistochemical study of nine cases. Human Pathol 1984;15:768-778.[Medline]
- Ducatman BS, Scheithauer BW. Malignant peripheral nerve sheath tumors with divergent differentiation Cancer 1984;54:1049-1057.[Medline]
- Bose AK, Deodhar AP, Duncan AJ. Malignant Triton tumor of the right vagus Ann Thorac Surg 2002;74:1227-1228.[Abstract/Free Full Text]
- Downey RJ, Mc Cormack P, Lo Cicero III J. Dissemination of malignant tumors after video-assisted thoracic surgery. a report of twenty-one cases. J Thorac Cardiovasc Surg 1996;111:954-960.[Abstract/Free Full Text]
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Abstract
Introduction
