Sacrococcygeal teratoma with nephroblastoma (Wilms' tumor): A variant of extragonadal teratoma in childhood. A histologic and ultrastructural study

The morphological features including the light and ultrastructural observations of a sacrococcygeal neoplasm in a 3‐year‐old girl are reported. Unlike the usual pattern of the malignant sacrococcygeal teratoma (embryonal carcinoma), this tumor was composed predominantly of nephroblastomatous tissue. Histologically, glomeruloid and tubular structures were identified in nests of undifferentiated epithelium. A loose, myxoid stroma surrounded these nests. Cartilage, foci of striated muscle, neuroglia, and glandular epithelium of respiratory and gastointestinal type were minor elements. The ultrastructural features were very similar to those previously described in Wilms' tumors of the kidney.