Clear cell sarcoma of the kidney: report of a case with mandibular metastasis simulating a benign myxomatous tumor.

The clear cell sarcoma of the kidney (CCSK) is one of the histologically unfavorable types of childhood renal tumors that has a propensity for osseous metastasis. We have presented the clinical and pathologic findings of the first well-documented case of a CCSK with mandibular metastasis, which was recognized approximately 18 months after the original diagnosis. Microscopically, the mandibular lesion had the features of a benign myxomatous neoplasm with the exception of occasional atypical spindle cells. Electron microscopic observation confirmed the undifferentiated nature of the neoplastic cells. It was concluded that the intensive chemotherapy that was administered to our patient very likely affected the histologic appearance of the mandibular metastasis as well as other recurrent lesions in the abdomen. Our review of the literature revealed only five previous examples of Wilms' tumor that had metastasized to the mandible. At least one of these earlier cases also represented a CCSK.