Malignant Triton Tumor (Malignant Peripheral Nerve Sheath Tumor With Rhabdomyoblastic Differentiation) Occurring in a Vascularized Free Flap Reconstruction Graft

Int J Surg Pathol. 2017 Aug;25(5):462-467. doi: 10.1177/1066896917700725. Epub 2017 Apr 7.


Malignant peripheral nerve sheath tumor (MPNST) is a rare form of sarcoma arising from Schwann cells or pluripotent cells of the neural crest. Malignant triton tumor (MTT) is a subtype of MPNST with a component of malignant rhabdomyoblasts in addition to malignant Schwann cells. MPNST and MTT are both aggressive malignancies that most commonly arise from large deep neurofibromas in patients with neurofibromatosis type 1 (NF-1). However, sporadic non-NF-1 cases of MTT have also been reported in the literature. We present a case of a 50-year-old African American male with no stigmata of NF-1 who developed a large mass in a free flap on the right calf. The free flap had been placed by plastic surgery 15 years previously following open right tibial and fibular fractures associated with a large soft tissue defect. Biopsy of the enlarging mass, followed by wide surgical excision, confirmed the pathology to be MTT. Although the development of a high-grade soft tissue sarcoma has been previously reported as a late complication of radiation therapy following free flap reconstructions, we believe this is the first reported case of sarcomatous transformation arising in a vascularized, free muscle transfer.

Keywords: free muscle flap; malignant Triton tumor; malignant peripheral nerve sheath tumor; rhabdomyoblasts; sarcoma.

Publication types

  • Case Reports

MeSH terms

  • Biopsy
  • Cell Differentiation
  • Cell Transformation, Neoplastic / pathology
  • Fibula / injuries
  • Fractures, Multiple / complications
  • Fractures, Multiple / surgery
  • Free Tissue Flaps / pathology*
  • Humans
  • Magnetic Resonance Imaging
  • Male
  • Middle Aged
  • Muscle Neoplasms / diagnostic imaging
  • Muscle Neoplasms / pathology*
  • Muscle Neoplasms / therapy
  • Muscle, Skeletal / pathology
  • Muscle, Skeletal / transplantation
  • Myoblasts, Skeletal / pathology
  • Neurilemmoma / diagnostic imaging
  • Neurilemmoma / pathology*
  • Neurilemmoma / therapy
  • Plastic Surgery Procedures / adverse effects*
  • Radiotherapy, Adjuvant
  • Sarcoma / pathology*
  • Sarcoma / therapy
  • Soft Tissue Injuries / etiology
  • Soft Tissue Injuries / surgery
  • Tibial Fractures / complications
  • Tibial Fractures / surgery
  • Tissue Transplantation / adverse effects*
  • Tissue Transplantation / methods
  • Tomography, X-Ray Computed