Developmental pattern of Thy-1 immunoreactivity in the human kidney and the application to pediatric renal neoplasms.

The localization of Thy-1, a surface membrane lipoglycoprotein, was investigated using a monoclonal antibody specific for human Thy-1 (HB-2S-1). The localization of Thy-1 during development was established in a series of five fetal, three childhood, and two adult normal kidneys. In this series, Thy-1 immunolocalization progressed from mesangial and endothelial cell staining in the 16- to 17-week fetuses to similar staining along with staining of the parietal epithelium of the capsule and proximal tubule staining in the 20- to 24-week fetuses. Glomerular mesangial cell and endothelial cell staining was absent by 9 months postnatally when the adult pattern of staining was apparent. The localization of Thy-1 during development was also compared with a series of pediatric renal tumors including 14 Wilms' tumors, 3 congenital mesoblastic nephromas, 1 clear cell sarcoma, and 1 pediatric renal cell carcinoma. Thy-1 staining was demonstrated in epithelial tubules of Wilms' tumors and in the spindle-shaped cells of congenital mesoblastic nephroma correlating with Thy-1 immunoreactivity in the kidney proximal tubule and fetal medullary stroma, respectively. Thy-1 staining was absent in the anaplastic epithelial Wilms' tumor, the renal cell carcinoma, and the clear cell sarcoma. This staining pattern fails to provide evidence that these tumors may arise from the medullary mesenchyme or the differentiated proximal convoluted tubule. These results show that Thy-1 is a renal differentiation marker and is useful in the characterization of tumors of renal development.