Skeletal muscle metastasis in a patient with Wilms tumor and multiple late recurrences.

ABSTRACT

Stage III Wilms tumor was diagnosed in a 9-year-old girl. Four and a half years after the treatment, which consisted of an operation, radiation therapy, and chemotherapy, the patient had a solitary metastasis in the liver, which was successfully treated with chemotherapy and surgical resection. Five years later, right lung metastases were eradicated by chemotherapy, radiation, and surgical resection. Three and a half years later, she had a metastasis in the left calf, for which she underwent surgical resection and received chemotherapy. This patient has several interesting features (1) multiple recurrences, two in the usual sites of metastasis and one in an extremely rare site, i.e., skeletal muscle; (2) long intervals between recurrences; and (3) unusual histopathologic features, i.e., gradual evolution from a triphasic Wilms tumor at the primary site, to a predominance of differentiated mucinous epithelium in the skeletal muscle metastasis.