A rare case of malignant triton tumor with pluridirectional differentiation.

An enlarging soft tissue mass was resected from the leg of a young man with neurofibromatosis type 1. Rhabdomyosarcomatous elements admixed with islands of osteoid and chondroid matrix was seen on microscopy. Based on immunohistochemistry, a malignant triton tumor, an uncommon subtype of peripheral nerve sheath tumor with rhabdomyosarcomatous elements, was diagnosed. The important feature of this neoplasm was that it showed pluridirectional differentiation to osteosarcoma and chondrosarcoma. This pathologic finding is rare and seen in only a few cases of all malignant triton tumors.