A Case of Malignant Peripheral Nerve Sheath Tumor with Rhabdomyoblastic Differentiation: Malignant Triton Tumor

Abstract

Malignant peripheral nerve sheath tumors (MPNST) constitute a rare variety of soft tissue sarcomas thought to originate from Schwann cells or pluripotent cells of the neural crest. Malignant triton tumor (MTT), a very rare, highly aggressive soft tissue tumor, is a subgroup of MPNST and is comprised of malignant Schwann cells coexisting with malignant rhabdomyoblasts. We herein report the case of a 24-year-old man who presented a subcutaneous mass in his right thigh. The mass was removed surgically in its entirety and radiation therapy was applied locally to prevent tumor regrowth. Nonetheless, the patient died 10 months after surgery from metastases to the lung and brain. He presented neither cafe-au-lait spots nor cutaneous neurofibromas. The histopathology showed a transition from a neurofibroma to an MTT, making this the second report of an MTT arising from a neurofibroma without neurofibromatosis type 1, an autosomal dominant disorder with which 50-70% of tumors reported in previous studies were associated. A histopathological examination using immunostaining with desmin confirmed this diagnosis. MTT has a poorer prognosis than MPNST and should therefore be regarded as a distinct clinical entity.

A case of retroperitoneal malignant triton tumor in a Nigerian boy

“…MTT occurring in patients with NF-1 is more common, usually more than 50% of the cases; however, there are some sporadic cases not associated with NF-1. [ 1 6 7 8 10 15 17 ] Some have been suggested to arise following irradiations. [ 6 ] Those associated with NF-1 have been found to occur more in younger male patients and are more aggressive as seen in the index case.…”

“…[ 6 ] Diagnosis is confirmed by histology with immunohistochemical studies for desmin, vimentin, actin, myoglobulin, and S-100 protein. [ 7 8 ] The main stay of treatment is complete excision where possible in addition to adjuvant radiotherapy and chemotherapy. [ 3 5 ] There are <10 reported cases of retroperitoneal MTT in literature out of which only one was in a child.…”

Sinonasal Malignant Triton Tumor: A Case Report with Historical and Surgical Review

“…The efficacy of neo-adjuvant and adjuvant radiochemotherapy in MTT remains inconclusive [27]; however, as for any sarcoma, resection of the tumor with wide margins followed by radiotherapy is recommended as the standard of care. Radical excision is the only feasible option available for recurrences as the tumor is predominately chemo-refractory.…”

“…It is poorly understood why skeletal muscle differentiation increases the aggressiveness of these tumors. These tumors are fast growing and are prone to local recurrence/hematologic metastases [27]. Traditional adverse prognostic factors include truncal location, tumor size >5 cm, local recurrence, NF-1 positivity, high-grade, and completeness of resection with negative surgical margins [1,21].…”

A rare case of intracranial malignant triton tumor arising in the middle cranial fossa: a case report and review of the literature

“…In a recent metanalysis, only 124 cases of MTT were reported between 1973 and 2010 in the English and French literature [24]. Since then, 38 further cases of MTT have been reported [9,10,11,[13][14][15]17,18,20,22,[25][26][27][31][32][33][34], of whom only few had an intracranial location [1,3,6,7,11,12,19,34,35]. About one half of cases are related to neurofibromatosis type 1 (NF-1), and previous exposure to radiation is a recognized risk factor [37].…”