Sarcomatous variant of Wilms' tumor. A light and immunohistochemical study of four cases.

Four cases of infantile sarcomatous renal tumors are reported. Rhabdomyoblastic differentiation was investigated in these tumors by the immunoperoxidase method using antimyoglobin sera. Rhabdomyoblastic cells were found in 2 cases and in a metastasis of one case in which the primary tumor was composed by undifferentiated cells negative for myoglobin stain. The histogenesis of these neoplasias is discussed, and it is suggested that they are a sarcomatous variant of Wilms' tumor.