Malignant Triton tumor. A case with protean histopathological patterns.

A case of malignant Triton tumor occurring in the leg of a 48-year-old woman with neurofibromatosis (von Recklinghausen's disease) is presented. The neoplasm was composed mainly of spindle-shaped cells forming interlacing fascicles with areas of massive necrosis. The important feature in this neoplasm was the presence of rhabdomyoblastic cells admixed with other cellular components. In addition, variable histologic features including solid, myxomatous, hemangiomatous, hemangiopericytomatous, epithelioid, and lymphomatous areas were identified. This variety has been recognized in malignant schwannomas, but not in malignant Triton tumors. There were discrete foci with each predominant histologic feature shown in a map of the neoplasm in which the distribution of those components is demonstrated based on the histology and immunohistochemistry. Satisfactory biopsy specimens are necessary for accurate diagnosis of malignant Triton tumor.