Clinicomorphologic features of a series of 10 cases of malignant triton tumors diagnosed over 10 years at a tertiary cancer hospital in Mumbai, India.

A rhabdomyoblastic differentiation in a malignant peripheral nerve sheath tumor is unusual and is termed as a malignant triton tumor. A series of 10 such cases with their clinicomorphological features, diagnosed over a 10-year period, is presented. The average age of occurrence was 30 years, with the maximum number of cases in the second decade and with male outnumbering female patients. More cases were seen in the setting of neurofibromatosis. On histology, 80% of the cases were of high grade. Distinct rhabdomyoblastic cells were identified in the areas of malignant peripheral nerve sheath tumor. Immunohistochemistry confirmed the neurogenic differentiation with varying S-100 expression and the rhabdomyoblastic differentiation with desmin and myoglobin positivity in all cases. Surgery with adequate margins constituted the treatment mainstay with adjuvant chemotherapy and/or radiotherapy in individual cases. On follow-up with 7 cases, 3 showed local recurrences, including one that, in addition to another 2 cases, showed lung metastasis. One patient died of the disease. This case along with another high-grade case displayed a diffuse Ki-67 and p53 positivity. Malignant triton tumor is an uncommon tumor associated with an aggressive behavior. Surgery with clear margins is the treatment mainstay. Adjuvant radiotherapy is effective.