These cells have a fibrillary cytoplasm surrounding round nuclei with coarse and heavy nuclear chromatin. These cells are surrounded by much larger polygonal cells that have open nuclear chromatin and abundant opaque cytoplasm that has granular melanin pigment. There is usually no hemorrhage, necrosis or increased mitoses. Immunohistochemistry
The lesional cells will show cross reactivity with several different families of immunohistochemistry markers (polyphenotypic), including neural, melanocytic, and epithelial. Large tumor cells: Keratin, vimentin, HMB-45, NSE, CD57
Small tumor cells: Synaptophysin, GFAP, NSE, CD57
There is usually a variable expression of EMA and S100 protein. Differential diagnoses
It is important in this age group to exclude other tumors that can have a similar appearance, such as rhabdomyosarcoma, lymphoma, Ewing sarcoma (primitive neuroectodermal tumor), or even a melanoma (although they are very very rare in infants). Management
Even though there is often a very dramatic and rapidly enlarging, destructive tumor, there is usually a benign clinical course after complete local excision (usually by partial maxillectomy) with clear or free surgical margins. In rare cases, chemotherapy may be used for recurrent or residual tumors. Overall, the outcome is good, although it is quite unpredictable, with about 30% of patients have a recurrence. In about 10% of cases, metastasis may be seen (lymph nodes, liver, bone and soft tissue). Epidemiology
This tumor is extremely rare, with fewer than 500 cases reported world wide. More than 95% of patients are less than 1 year of age at presentation, with about 80% less than 6 months. Females are affected more often than males (2:1).
Malignant triton tumor (MTT) is a relatively rare, aggressive tumor made up of both malignant schwannoma cells and malignant rhabdomyoblasts. It is classified as a malignant peripheral nerve sheath tumor with rhabdomyosarcomatous differentiation.The unusual name "triton" was first used in reference to observation of supernumerary limbs containing bone and muscle growing on the backs of triton salamanders after the implantation of sciatic nerve tissue. Diagnosis
There are three diagnostic criteria proposed:
The tumor arises along a peripheral nerve, or in a ganglioneuroma, or in a patient with neurofibromatosis type 1 (NF1), or has a metastatic character. The growth characteristics of the tumor is typical for a Schwann cell tumor. Rhabdomyoblasts arise within the body of the tumor. Treatment
References
Bibliography
Stasik CJ, Tawfik; Tawfik, O (2006). "Malignant peripheral nerve sheath tumor with rhabdomyosarcomatous differentiation (malignant triton tumor)". Arch Pathol Lab Med. 130 (12): 1878–81. doi:10.5858/2006-130-1878-MPNSTW. PMID 17149968.