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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 byneurofibromatosis: A case report

Abdullah Merter a, *, Kerem Basarır b, Yusuf Yıldız b, Yener Sa�glık b

a Afsin State Hospital, Orthopedic Clinic, Kahramanmaras, Turkeyb Ankara University, School of Medicine, Ibn-i Sina Hospital, Department of Orthopedics, Oncology Section, Ankara, Turkey

a r t i c l e i n f o

Article history:Received 8 February 2017Received in revised form31 May 2017Accepted 30 July 2017Available online 27 October 2017

Keywords:Malignant peripheral nerve sheath tumorGluteal regionTriton tumor

* Corresponding author. Yesilyurt Mh. AfsinKahramanmaras, Turkey.

E-mail address: dr.merter@gmail.com (A. Merter).Peer review under responsibility of Turkish Asso

Traumatology.

http://dx.doi.org/10.1016/j.aott.2017.07.0051017-995X/© 2017 Turkish Association of Orthopaedic(http://creativecommons.org/licenses/by-nc-nd/4.0/).

a b s t r a c t

Malignant triton tumor (MTT) is a rare variant of malignant peripheral nerve sheath tumor (MPNST)made up of both malignant schwannoma cells and malignant rhabdomyoblasts.

A 26-years-old male patient was admitted with an asymptomatic gluteal mass. Magnetic resonanceimaging showed heterogeneous soft tissue mass and he underwent open biopsy. Malignant peripheralnerve sheath tumor was diagnosed. He was given adjuvant chemotherapy following the removal of thetumor with hip disarticulation. The tumor was diagnosed as “malignant triton tumor” based on path-ological examination including immunohistochemical studies. There were no signs of metastasis butrecurrence was observed at 9 months follow up.

MTT is usually associated with Neurofibromatosis 1 and located in head, neck region. In this casesporadic involvement of gluteal region and aggressive behavior of the lesion despite radical surgery wasdemonstrated.© 2017 Turkish Association of Orthopaedics and Traumatology. Publishing services by Elsevier B.V. This isan open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/

4.0/).

Introduction

Malignant “Triton” tumor (MTT) is a rare subtype of malignantperipheral nerve sheath tumor (MPNST) characterized by malig-nant schwannoma with rhabdomyosarcoma. This compositeneoplasm was initially introduced by Masson and Martin in 1938and this tumor is extremely rare, with fewer than 100 cases re-ported to date.1 It occurs predominantly in the head, neck andtrunk. The diagnosis based on the presence of rhabdomyoblasts andmalignant Schwann cells.2 Head and neck region is the mostfrequent site of involvement with one third of the lesions, followedby trunk and lower extremities respectively.3 Head and necklocalization seem to have an infrequent association withNerofibromatosis-1 (NF1) when compared to other localizations. Itis usually seen in individuals younger than 35 years of age MTTcarries a much worse prognosis than MPNST with an expected 5-year survival rate of 12.5%.4,5 Sporadic involvement of the glutealregion without NF1 hasn't been described yet in the literature.

Devlet Hastanesi, Afsin,

ciation of Orthopaedics and

s and Traumatology. Publishing se

In this article, we report a case of a Malignant “Triton” tumor inthe gluteal region of a male without Nerofibromatosis-1 with 57months follow up.

Case presentation

A 26-year-old male patient was presented with a 6 monthshistory of right buttock pain that was exacerbated with movement.There was no history of preceding trauma or accident. There was nofamily history of central nervous system neoplasia or of neurofi-bromatosis types 1 or 2. The physical examination revealed that apainful limp and pain with deep palpation. His neurologic exami-nation was normal. A radiographic image of the pelvis demon-strated an increase in soft tissue density adjacent to right iliac wing.Magnetic resonance imaging of pelvis demonstrated a large softtissue mass in the right gluteal region close to the sciatic nerve(Fig. 1). The 5 � 6 � 7 cm mass had low signal intensity on T1, pri-marily high signal on T2, and diffuse enhancement with gadolin-ium. There was a central focus of low signal intensity on the T2 andgadolinium-enhanced images (Fig. 2). Open biopsy was performedand histological examination demonstrated a lesion consisted ofcells showing either rhabdomyoblastic or neuronal differentiationwhich was characteristic for malignant triton tumor. Investigationsincluding computerized tomography of thorax ruled out a

rvices by Elsevier B.V. This is an open access article under the CC BY-NC-ND license

Fig. 1. A large soft tissue mass in the right gluteal region close to the sciatic nerve onT1 sequence.

Fig. 2. Central focus of low signal intensity on sagittal T2 sequence.

Fig. 3. Microscopic view of excision material.

A. Merter et al. / Acta Orthopaedica et Traumatologica Turcica 52 (2018) 236e239 237

metastatic disease. The patient subsequently underwent furthersurgery to ensure full excision of the tumor. A wide resection wasperformed via hip disarticulation with anterior flap. Postsurgicalrecovery was uneventful. Microscopical examination revealednumerous 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, desminpositivity which was also consistent with the diagnosis of MTT.Surgical margins were clear. Pathological examination includingimmunohistochemical analysis confirmed the diagnosis of MTT(Fig. 3). Hewas started on combination chemotherapy of ifosfamide

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 thencontinued with ifosfamide and mesna for the rest of the two cycleswithout adriamycin. The patient was followed up by 6 weekly pe-riods and the surgical field checked with MRI every 3 months. Ninemonths after initial wide resection, the patient presented withcontinuing pain. The follow-up MRI demonstrated a 3 � 4 � 1 cmrecurrent mass nearby the operative bed of the previously resectedlesion. The mass had similar signal characteristics with low signalintensity on T1 and high signal intensity on T2 (Fig. 4). PET/CT scanalso demonstrated a recurrent mass in the gluteal region (Fig. 5).Radiation therapy was applied with a total dose of 65.4 Gy, withinitial photon fields, followed by shrinking fields with electronswith 33 dose fractions during the course of 2 months. He was un-derwent secondwide resection after radiotherapy. The pathologicalinvestigation was the same as the first one and surgical marginswere clear. He has followed up in our department and has no evi-dence of disease recurrence 4 years after his treatment.

Discussion

Malignant peripheral nerve sheath tumor is a neoplasm thatarises primarily in the peripheral nerves and accounts for 5e10% ofall soft tissue sarcomas.1 The termMalignant TritonTumor is used fortumors exhibiting the features of an MPNST and containing rhab-domyoblastic elements.4 The disorder was named for the Tritonsalamander, which is capable of regenerating limbs consisting ofboth muscle and nerve tissue after the cut end of the sciatic nerve isimplanted into the soft tissue of its back.3 The pathogenesis ofMTT isunknown, the presence of both neural cells and rhabdomyoblastshave led some to hypothesize that both cellular components derivefrom less differentiated neural crest cells that have bothmesodermaland ectodermal potential and others points out direct evidence forthe potential of schwannoma cells to exhibit myogenic differentia-tion.6 Masson and Martin initially postulated that divergent myoiddifferentiation could occur in neoplastic neuroectodermal cells butthere are it seems likely that both cell lines originate from less well-differentiated neural crest cells.7,8 Cytogenetic studies reveal certainabnormalities in these tumors including common breakpoints in Chr7, 11 and loss of Chr 22.5,8

Almost seventy percent of these tumors were diagnosed in pa-tients with von Recklinghausen's disease (NF1) displayed a markedmale predominance, young age, and infrequent head and neckpresentation, whereas the remaining sporadic 30% were older and

Fig. 4. 3 � 4 � 1 cm recurrent mass nearby the operative bed of the previouslyresected lesion.

Fig. 5. PET/CT scan image of the patient.

A. Merter et al. / Acta Orthopaedica et Traumatologica Turcica 52 (2018) 236e239238

had a female predominance.4 MTT may also arise after radiationtherapy.9 The most frequent localization was head and neck regionfollowed by upper, lower extremities, retroperitonium, buttock andtrunk.10 The mean age is 38 years in sporadic cases and younger incases associated with neurofibromatosis.11,12 Our patient was asporadic case of 26 years-old male with gluteal involvementwithout any evidence of NF 1 and no history of radiation therapywhich was quite rare.

The presenting symptom is usually a progressively enlargingmass that may give rise to neurologic symptoms. Radiologic fea-tures of MTT are similar to that of MPNST. It includes soft tissuemass with or without calcification on direct radiography. Anasymptomatic growing mass without neurological impairment wasthe major complaint in our patient and a soft tissue mass wasobserved on direct x-ray without calcification. Magnetic resonanceimaging is themost useful diagnostic tool in the examination of softtissue 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 ourcase showing low intensity on T1 weighted images and high in-tensity on T2 weighted images. The heterogenicity indicated areasof necrosis and hemorrhage.

On histopathologic examination, MTT appears as a tumorcomposed of sheets of interlacing spindle cells together with largepleomorphic rhabdomyoblastic cells.3 MTT can easily be over-looked if the immunohistochemical examination does not includepan muscle actin or desmin.2 Immunohistochemically s-100 posi-tivity for MPNST and desmin positivity for rhabdomyoblastic ele-ments aids the diagnosis.3 MPNST is often seen in patients withneurofibromatosis 1 (NF1) in 70% of the cases and it may also occursporadically.

The prognosis of MTT is much worse than sporadic MPNST.4 Thechoice of treatment for MTT is radical tumor excision with widemargins. Adjuvant chemotherapy and radiation therapy are sug-gested by several authors for long-term survival.10 The head andneck region and in the upper and lower extremities have a betterprognosis than tumors located in retroperitonium, buttock ortrunk.13,14 Local recurrence time is reported 6 months.15 In our casetotal surgical excision was performed and followed by post-operative chemotherapy.

In conclusion, MTT is a rare tumor which should be differenti-ated fromMPNST because of its more aggressive behavior. Sporadicinvolvement of peripheral localizations without NF1 may occursuch as gluteal region and have very aggressive behavior despiteradical surgery. Complete surgical removal followed by radiationtherapy and/or chemotherapy is essential for long term survival.

References

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3. James JA, Bali NS, Sloan P, Shanks JH. Low Grade malignant triton tumor of theoral cavity. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2003 Jun;95(6):699e704.

4. Brooks JS, Freeman M, Enterline HT. Malignant “Triton” tumors: natural historyand immunohistochemistry of nine cases with literature review. Cancer. 1985Jun 1;55(11):2543e2549.

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