Malignant “Triton” tumors. Natural history and immunohistochemistry of nine new cases with literature review

TLDR

Malignant schwannomas with rhabdomyoblastic differentiation, termed malignant “Triton” tumors (MTT), are rare and were notably observed as a polypoid esophageal mass in this study. The study aims to delineate the natural history of MTT by analyzing 9 new cases alongside 27 reported cases, totaling 36. Rhabdomyoblastic differentiation was confirmed by myoglobin immunohistochemistry, and patients were stratified into Von Recklinghausen’s Neurofibromatosis (Group I) and sporadic (Group II) cohorts. Group I comprised over 70% of cases, predominantly young males with head‑and‑neck tumors, whereas Group II were older females with trunk lesions; both groups experienced frequent local recurrence, a 5‑year survival of 12%, and an aggressive course comparable to VRN sarcomas, largely attributable to the high prevalence of Grade III histology.

Abstract

Malignant schwannomas with rhabdomyoblastic differentiation have been termed malignant "Triton" tumors (MTT). To define the natural history of MTT, we have analyzed our experience (9 cases, the largest series reported) in combination with the 27 previously described in the literature (total 36 cases). This study was initiated due to the unusual presentation of MTT as a polypoid esophageal mass. Rhabdomyoblastic differentiation in these tumors was confirmed using myoglobin immunohistochemistry. Two groups of patients were identified: those with Von Recklinghausen's Neurofibromatosis (Group I, VRN cases); and those without (Group II, sporadic, non-VRN cases). Group I patients accounted for over 70% of cases and displayed a marked male predominance, young age, and common head and neck presentation. By contrast, Group II patients were older, had a female predominance, and tumors frequently located on the trunk. Both groups fared equally poorly: local recurrence was common and the 5-year survival rate for all cases was 12%. Our data support the view that the natural history of MTT, whether in VRN patients or not, is much more aggressive than sporadic malignant schwannoma and similar to VRN sarcomas in general. This poor outlook could not be attributed to site; rather, it appeared to reflect the high frequency of Grade III histology in this disease.