Analysis of clinical features and prognosis of malignant triton tumor: A report of two cases and literature review

Abstract

Malignant triton tumor (MTT) is a malignant peripheral nerve sheath tumor with rhabdomyoblastic differentiation. The prognosis of patients is poor, and due to its rarity, large case studies are lacking. The aim of this study is to describe the clinical features and identify potential prognostic factors. Two patients with MTT in the head and neck treated at our department are reported. A literature search revealed another 198 published cases. All of these cases then went through a retrospective analysis. The ratio of male-to-female incidence was 1.5:1, and the median age at diagnosis was 29 years. In 41.7% of cases it occurred in patients with neurofibromatosis type 1. The five-year survival of MTT was found to be just 35%. Cox proportional hazards analysis revealed that complete resection (hazard ratio, 0.396; P=0.032) and metastases (hazard ratio, 3.188; P=0.004) were associated with mortality, indicating that complete resection may lead to a longer life span, and that the existence of metastasis suggested a worse prognosis for patients with MTT.

Keywords: malignant triton tumor; prognosis; surgery; survival analyses.

Figure 1.

Magnetic resonance imaging (MRI) and computed tomography (CT) scan results of the malignant triton tumor (MTT) cases in our hospital. (A) MRI results revealed that the mass had long or isodense T1 signals. (B, C) The mass demonstrated long T2 signals. In certain images, there are ring or linear forms, as a type of isolation strip, with isodense T2 signals, which are likely due to necrosis and hemorrhage in the mass. (D) MRI revealed isodense T1 signals in the tonsil MTT. (E) Gadolinium-diethylenetriamine pentaacetic acid-enhanced MRI indicated an enhancement of the mass with a distinct lobulated margin in the parapharyngeal space MTT. (F) Enhanced spiral CT scanning of the parapharyngeal space MTT.

Figure 2.

Images of hematoxylin and eosin (HE) staining and immunohistochemistry results of malignant triton tumor (MTT). (A) Images of HE staining. Large pleomorphic rhabdomyoblastic cells with abundant eosinophilic cytoplasm are embedded in a spindle cell tumor with a fine fibrillary matrix. (B-H) Immunohistochemistry results of MTT. The immunohistochemistry results were positive for NF(+), myogenin(++), Bcl-2(+), CD34(+), CD99(+), desmin(+) and vimentin(+). Magnification, ×400.

Figure 3.

Age distribution and survival analysis of MTT patients. (A) Results revealed that patients with NF-1 were most common in the 20–39 age group while those without NF-1 had two peaks in the 20s and 50s. (B) Life span analysis revealed that the 1-, 2- and 5-year survival rates were 69%, 48% and 35%, respectively. (C and D) Kaplan-Meier survival analysis of the data for the 133 cases with follow-up revealed that complete resection (P=0.010) and metastasis (P<0.001) had a statistically significant effect on the survival curves.