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

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.