Malignant Triton Tumor of the Gluteal Region in a Patient Unaffected by Neuroﬁbromatosis: a Case Report

Acta Orthopaedica et Traumatologica Turcica 52 (2018) 236e239

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Acta Orthopaedica et Traumatologica Turcica

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Malignant triton tumor of the gluteal region in a patient unaffected by neuroﬁbromatosis: A case report

* Abdullah Merter a, , Kerem Bas¸arır b, Yusuf Yıldız b, Yener Sagl ık b a Afsin State Hospital, Orthopedic Clinic, Kahramanmaras, Turkey b Ankara University, School of Medicine, Ibn-i Sina Hospital, Department of Orthopedics, Oncology Section, Ankara, Turkey article info abstract

Article history: Malignant triton tumor (MTT) is a rare variant of malignant peripheral nerve sheath tumor (MPNST) Received 8 February 2017 made up of both malignant schwannoma cells and malignant rhabdomyoblasts. Received in revised form A 26-years-old male patient was admitted with an asymptomatic gluteal mass. Magnetic resonance 31 May 2017 imaging showed heterogeneous soft tissue mass and he underwent open biopsy. Malignant peripheral Accepted 30 July 2017 nerve sheath tumor was diagnosed. He was given adjuvant chemotherapy following the removal of the Available online 27 October 2017 tumor with hip disarticulation. The tumor was diagnosed as “malignant triton tumor” based on pathological examination including immunohistochemical studies. There were no signs of metastasis but Keywords: Malignant peripheral nerve sheath tumor recurrence was observed at 9 months follow up. ﬁ Gluteal region MTT is usually associated with Neuro bromatosis 1 and located in head, neck region. In this case Triton tumor sporadic involvement of gluteal region and aggressive behavior of the lesion despite radical surgery was demonstrated. © 2017 Turkish Association of Orthopaedics and Traumatology. Publishing services by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

Introduction In this article, we report a case of a Malignant “Triton” tumor in the gluteal region of a male without Nerofibromatosis-1 with 57 Malignant “Triton” tumor (MTT) is a rare subtype of malignant months follow up. peripheral nerve sheath tumor (MPNST) characterized by malignant schwannoma with rhabdomyosarcoma. This composite Case presentation neoplasm was initially introduced by Masson and Martin in 1938 and this tumor is extremely rare, with fewer than 100 cases re- A 26-year-old male patient was presented with a 6 months ported to date.1 It occurs predominantly in the head, neck and history of right buttock pain that was exacerbated with movement. trunk. The diagnosis based on the presence of rhabdomyoblasts and There was no history of preceding trauma or accident. There was no malignant Schwann cells.2 Head and neck region is the most family history of central nervous system neoplasia or of neurofi- frequent site of involvement with one third of the lesions, followed bromatosis types 1 or 2. The physical examination revealed that a by trunk and lower extremities respectively.3 Head and neck painful limp and pain with deep palpation. His neurologic exami- localization seem to have an infrequent association with nation was normal. A radiographic image of the pelvis demon- Nerofibromatosis-1 (NF1) when compared to other localizations. It strated an increase in soft tissue density adjacent to right iliac wing. is usually seen in individuals younger than 35 years of age MTT Magnetic resonance imaging of pelvis demonstrated a large soft carries a much worse prognosis than MPNST with an expected 5- tissue mass in the right gluteal region close to the sciatic nerve year survival rate of 12.5%.4,5 Sporadic involvement of the gluteal (Fig. 1). The 5 Â 6 Â 7 cm mass had low signal intensity on T1, pri- region without NF1 hasn't been described yet in the literature. marily high signal on T2, and diffuse enhancement with gadolinium. There was a central focus of low signal intensity on the T2 and gadolinium-enhanced images (Fig. 2). Open biopsy was performed * Corresponding author. Yesilyurt Mh. Afsin Devlet Hastanesi, Afsin, and histological examination demonstrated a lesion consisted of Kahramanmaras, Turkey. E-mail address: [email protected] (A. Merter). cells showing either rhabdomyoblastic or neuronal differentiation Peer review under responsibility of Turkish Association of Orthopaedics and which was characteristic for malignant triton tumor. Investigations Traumatology. including computerized tomography of thorax ruled out a http://dx.doi.org/10.1016/j.aott.2017.07.005 1017-995X/© 2017 Turkish Association of Orthopaedics and Traumatology. Publishing services by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). A. Merter et al. / Acta Orthopaedica et Traumatologica Turcica 52 (2018) 236e239 237

2 g/m2 with mesna 2 g/m2 alternating with adriamycin 75 g/m2 every other week for first two cycles 4 weeks apart and then continued with ifosfamide and mesna for the rest of the two cycles without adriamycin. The patient was followed up by 6 weekly pe- riods and the surgical field checked with MRI every 3 months. Nine months after initial wide resection, the patient presented with continuing pain. The follow-up MRI demonstrated a 3 Â 4 Â 1cm recurrent mass nearby the operative bed of the previously resected lesion. The mass had similar signal characteristics with low signal intensity on T1 and high signal intensity on T2 (Fig. 4). PET/CT scan also demonstrated a recurrent mass in the gluteal region (Fig. 5). Radiation therapy was applied with a total dose of 65.4 Gy, with initial photon fields, followed by shrinking fields with electrons with 33 dose fractions during the course of 2 months. He was underwent second wide resection after radiotherapy. The pathological investigation was the same as the first one and surgical margins were clear. He has followed up in our department and has no evidence of disease recurrence 4 years after his treatment.

Discussion

Fig. 1. A large soft tissue mass in the right gluteal region close to the sciatic nerve on Malignant peripheral nerve sheath tumor is a neoplasm that T1 sequence. arises primarily in the peripheral nerves and accounts for 5e10% of all soft tissue sarcomas.1 The term Malignant Triton Tumor is used for tumors exhibiting the features of an MPNST and containing rhabdomyoblastic elements.4 The disorder was named for the Triton salamander, which is capable of regenerating limbs consisting of both muscle and nerve tissue after the cut end of the sciatic nerve is implanted into the soft tissue of its back.3 The pathogenesis of MTT is unknown, the presence of both neural cells and rhabdomyoblasts have led some to hypothesize that both cellular components derive from less differentiated neural crest cells that have both mesodermal and ectodermal potential and others points out direct evidence for the potential of schwannoma cells to exhibit myogenic differentiation.6 Masson and Martin initially postulated that divergent myoid differentiation could occur in neoplastic neuroectodermal cells but there are it seems likely that both cell lines originate from less well- differentiated neural crest cells.7,8 Cytogenetic studies reveal certain abnormalities in these tumors including common breakpoints in Chr 7, 11 and loss of Chr 22.5,8 Almost seventy percent of these tumors were diagnosed in patients with von Recklinghausen's disease (NF1) displayed a marked male predominance, young age, and infrequent head and neck presentation, whereas the remaining sporadic 30% were older and

Fig. 2. Central focus of low signal intensity on sagittal T2 sequence. metastatic disease. The patient subsequently underwent further surgery to ensure full excision of the tumor. A wide resection was performed via hip disarticulation with anterior ﬂap. Postsurgical recovery was uneventful. Microscopical examination revealed numerous large pleomorphic cells with abundant cytoplasm con- trasting with the pale staining cytoplasm of the Schwann cells. Immunohistochemical analysis showed S-100, Leu-7, CD57, desmin positivity which was also consistent with the diagnosis of MTT. Surgical margins were clear. Pathological examination including immunohistochemical analysis conﬁrmed the diagnosis of MTT (Fig. 3). He was started on combination chemotherapy of ifosfamide Fig. 3. Microscopic view of excision material. 238 A. Merter et al. / Acta Orthopaedica et Traumatologica Turcica 52 (2018) 236e239

Fig. 4. 3 Â 4 Â 1 cm recurrent mass nearby the operative bed of the previously resected lesion. had a female predominance.4 MTT may also arise after radiation therapy.9 The most frequent localization was head and neck region followed by upper, lower extremities, retroperitonium, buttock and trunk.10 The mean age is 38 years in sporadic cases and younger in cases associated with neurofibromatosis.11,12 Our patient was a sporadic case of 26 years-old male with gluteal involvement without any evidence of NF 1 and no history of radiation therapy which was quite rare. The presenting symptom is usually a progressively enlarging mass that may give rise to neurologic symptoms. Radiologic features of MTT are similar to that of MPNST. It includes soft tissue mass with or without calcification on direct radiography. An asymptomatic growing mass without neurological impairment was the major complaint in our patient and a soft tissue mass was observed on direct x-ray without calcification. Magnetic resonance imaging is the most useful diagnostic tool in the examination of soft tissue malignancies. The lesion usually is hyperintense on T2- weighted images and low or iso intense on T1-weighted images. A heterogenous mass with indistinct margins was observed in our case showing low intensity on T1 weighted images and high intensity on T2 weighted images. The heterogenicity indicated areas of necrosis and hemorrhage. Fig. 5. PET/CT scan image of the patient. On histopathologic examination, MTT appears as a tumor composed of sheets of interlacing spindle cells together with large In conclusion, MTT is a rare tumor which should be differenti- 3 pleomorphic rhabdomyoblastic cells. MTT can easily be over- ated from MPNST because of its more aggressive behavior. Sporadic looked if the immunohistochemical examination does not include involvement of peripheral localizations without NF1 may occur 2 pan muscle actin or desmin. Immunohistochemically s-100 posi- such as gluteal region and have very aggressive behavior despite tivity for MPNST and desmin positivity for rhabdomyoblastic ele- radical surgery. Complete surgical removal followed by radiation 3 ments aids the diagnosis. MPNST is often seen in patients with therapy and/or chemotherapy is essential for long term survival. neurofibromatosis 1 (NF1) in 70% of the cases and it may also occur sporadically. References The prognosis of MTT is much worse than sporadic MPNST.4 The choice of treatment for MTT is radical tumor excision with wide 1. Enzinger FM, Weiss SW. Soft Tissue Tumors. 2nd ed. St. Louis: C.V. Mosby margins. Adjuvant chemotherapy and radiation therapy are sug- Company; 1988:1230e1240. gested by several authors for long-term survival.10 The head and 2. Ducatman BS, Scheithauer BW. Malignant peripheral nerve sheath tumor with divergent differentiation. Cancer. 1984 Sep 15;54(6):1049e1057. neck region and in the upper and lower extremities have a better 3. James JA, Bali NS, Sloan P, Shanks JH. Low Grade malignant triton tumor of the prognosis than tumors located in retroperitonium, buttock or oral cavity. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2003 Jun;95(6): trunk.13,14 Local recurrence time is reported 6 months.15 In our case 699e704. 4. Brooks JS, Freeman M, Enterline HT. Malignant “Triton” tumors: natural history total surgical excision was performed and followed by post- and immunohistochemistry of nine cases with literature review. Cancer. 1985 operative chemotherapy. Jun 1;55(11):2543e2549. A. Merter et al. / Acta Orthopaedica et Traumatologica Turcica 52 (2018) 236e239 239

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