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


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 resonance imaging showed heterogeneous soft tissue mass and he underwent open biopsy. Malignant peripheral nerve sheath tumor was diagnosed. He was given adjuvant chemotherapy following the removal of the 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 recurrence was observed at 9 months follow up.

MTT is usually associated with Neurofibromatosis 1 and located in head, neck region. In this case sporadic involvement of gluteal region and aggressive behavior of the lesion despite radical surgery was demonstrated.


Malignant “Triton” tumor (MTT) is a rare subtype of malignant peripheral nerve sheath tumor (MPNST) characterized by malignant schwannoma with rhabdomyosarcoma. This composite neoplasm was initially introduced by Masson and Martin in 1938 and this tumor is extremely rare, with fewer than 100 cases reported to date.1 It occurs predominantly in the head, neck and trunk. The diagnosis based on the presence of rhabdomyoblasts and malignant Schwann cells.2 Head and neck region is the most frequent site of involvement with one third of the lesions, followed by trunk and lower extremities respectively.3 Head and neck localization seem to have an infrequent association with Nerofibromatosis-1 (NF1) when compared to other localizations. It is usually seen in individuals younger than 35 years of age MTT carries a much worse prognosis than MPNST with an expected 5-year survival rate of 12.5%.45 Sporadic involvement of the gluteal region without NF1 hasn’t been described yet in the literature.

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

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