Malignant triton tumour of the sinonasal tract: Case report and literature review

Computed tomography imaging features of malignant 'triton' tumor to facilitate its clinical diagnosis: report of two cases

Background

Malignant ‘triton’ tumor is an extremely rare subtype of malignant periphery nerve sheath tumors. Clinical diagnosis of malignant triton tumor is difficult before surgery due to its low incidence and the lack of knowledge. Therefore, to describe and summarize the CT imaging characteristics of malignant triton tumor is of great assistance for early and preoperative diagnosis.

Case presentation

Two cases suspected of MTT by CT scan before operation were closely observed. The diagnosis of malignant triton tumor was eventually confirmed by immunochemical assay, which verified speculation of CT scans. Huge, irregular, well-circumscribed lobulated mass-like shadows can be observed from these patients by CT scans. Besides, heterogeneity of density within the body of tumor was well-established by CT scans, together with linear septum. Meanwhile, CT scans demonstrated that calcifications were remarkable at the margin of tumor body.

Conclusions

Some CT image features from two cases were presented as a reference for the preoperative consideration of MTT: (i) enormity of mass-like shadow; (ii) presence of well-circumscribed lobulated shape; (iii) septum within the well-defined mass accompanied with hemorrhage, necrosis and cystic changes as well as calcification, especially within neurofibromatosis type 1 patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12880-022-00848-9.

Malignant triton tumour (MTT) of the lung with metastasis to the proximal femur

A 65-year-old female patient has a history of malignant triton tumour of the right upper lobe of the lung. She underwent right upper lobectomy and lymphadenectomy in May 2018. She presented in November 2019 with pathological fracture of the left proximal femur. It was not associated with neurofibromatosis. We decided to do an excisional biopsy of the mass and proximal femoral replacement followed by radiotherapy. Four months later, she presented with local recurrence. We organised a multidisciplinary team between the orthopaedic, histopathology and oncology teams. Then, we decided to treat her with chemotherapy. After 2 months of follow-up, she responded well to the chemotherapy with no further deterioration of her condition.

Triton tumor of the orbit

A triton tumor is a malignant peripheral nerve sheath tumor (MPNST) with rhabdomyomatous differentiation These tumors account for 5% of MPNSTs and have an extremely poor prognosis. We describe the case of a 14-year-old girl who presented with a history of painful, progressive protrusion of her right eye with a diminution of vision for the past five years. She had been diagnosed as having an embryonal rhabdomyosarcoma of the right orbit, and she had undergone surgical debulking followed by chemotherapy and radiotherapy. Despite undergoing multiple modalities of treatment, she had several recurrences prior to this consultation. We reviewed her histology slides. HPE features were consistent with a malignant triton tumor with cartilage and osseous differentiation. Immunohistochemistry was done to confirm the diagnosis. In view of the aggressive nature of the tumor with multiple recurrences; she was advised palliative radical excision to reduce the tumor burden.

A case of recurrent malignant triton tumor successfully treated with radiotherapy

A 15-year-old female was previously admitted to another hospital because of painless swelling of the lateral right nasal ala for 2 months. Magnetic resonance imaging revealed an expansive enhancing lesion in close proximity to the anterior surface of the right maxillary sinus and lateral wall of the right nasal cavity. Tumor extirpation was performed via the supragingival transantral approach under general anesthesia. Histopathological study revealed a malignant triton tumor (MTT) arising from the nasal vestibule. The patient was referred to our department for consultation regarding additional treatment. Because the surgical margin was positive and MTT has high malignant potential, we recommended expansion re-surgical treatment following immediate free-flap reconstruction and postoperative radiotherapy, but family consent was not obtained. Tumor regrowth was noted 1 month after her first visit to our department. The patient and her family accepted radiotherapy instead of surgical treatment. Complete remission was achieved by radiotherapy alone. No local recurrence or distant metastasis was observed for 30 months after radiotherapy. The conventional mode of treatment for MTT is radical excision followed by high-dose radiotherapy. However, this case is remarkable because our patient experienced complete remission by simple radiotherapy.

Malignant Triton Tumors in Sisters with Clinical Neurofibromatosis Type 1

Malignant triton tumors (MTTs) are rare and aggressive sarcomas categorized as a subgroup of malignant peripheral nerve sheath tumors (MPNSTs). MTTs arise from Schwann cells of peripheral nerves or existing neurofibromas and have elements of rhabdomyoblastic differentiation. We report the occurrence of MTTs in two sisters. The first patient is a 36-year-old female who presented with left sided chest wall swelling. She also had clinical features consistent with neurofibromatosis type 1 (NF-1). Debulking of the mass showed high-grade malignant peripheral nerve sheath tumor with skeletal muscle differentiation (MTT). The patient was treated with ifosfamide and adriamycin along with radiation. Four years after treatment, she still has no evidence of disease recurrence. Her sister subsequently presented to us at the age of 42 with left sided lateral chest wall pain. Imaging showed a multicompartmental retroperitoneal cystic mass with left psoas involvement. The tumor was resected and, similarly to her sister, it showed high-grade malignant peripheral nerve sheath tumor with rhabdomyoblastic differentiation (MTT). The patient was started on chemotherapy and radiation as described above.