ABSTRACT
Malignant triton tumor [MTT] is a tumor arising from Schwann cells with divergent rhabdomyoblastic differentiation.It is a relatively rare and aggressive variant of malignant peripheral nerve sheath tumor [MPNST]. We present a case of a 33 years old male with thigh swelling. Surgical excision was done followed by histopathological and immunohistochemical [IHC] workup which revealed a tumor showing two types of cell populations including pleomorphic spindle cells and large cells with pleomorphic eccentric nuclei. Spindle cells showed positivity for S-100 IHC stain confirming their neural origin while large cells with eccentric nuclei showed positivity for desmin and myogenin IHC stains confirming their rhabdomyoblastic origin. Hence, the diagnosis of MTT was made. A 5 years survival rate for MTT is 5-15% compared to 50-60% for MPNST. Considering it is a rare entity with aggressive clinical behavior and poor prognosis, correct diagnosis is essential that can be achieved by careful histological and IHC evaluation