Diagnostic utility of nestin expression in pediatric tumors in the region of the kidney.

Nestin is an intermediate filament that was first identified in neuroepithelial stem cells. During embryogenesis, nestin is expressed in a number of cell types, including neural crest cells and developing myocytes. We have recently shown that nestin is expressed in human podocytes and nephrogenic blastema. We sought to determine the utility of nestin expression in distinguishing pediatric tumors in the region of the kidney. Cases studied included Wilms tumor (n=24), nephroblastomatosis (n=6), renal cell carcinoma (n=19), renal clear cell sarcoma (n=9), mesoblastic nephroma (n=9), neuroblastoma (n=11), malignant rhabdoid tumor (n=8 including 2 renal), Ewing sarcoma (n=16 including 1 renal, 7 soft tissue, and 8 bone), intra-abdominal desmoplastic small round cell tumor (n=5), and rhabdomyosarcoma (n=8, all extrarenal). Nestin expression was assessed semiquantitatively by immunohistochemistry and then scored as positive or negative. All cases of Wilms tumor, mesoblastic nephroma, rhabdomyosarcoma, neuroblastoma, malignant rhabdoid tumor, and desmoplastic small round cell tumor were nestin-positive. In Wilms tumor and nephroblastomatosis, nestin was expressed in blastema and glomeruloid structures, but not tubules. In neuroblastoma, positive staining was detected regardless of degree of differentiation. The majority of Ewing sarcoma and renal cell carcinoma were negative. Expression in clear cell sarcoma was variable with 5 cases negative and 4 cases positive. Thus, nestin is a highly sensitive, but nonspecific, marker of Wilms tumor in the context of tumors that may occur in or around the kidney. Nestin reactivity may be useful in differentiating Wilms tumor from Ewing sarcoma, renal cell carcinoma, or nestin-negative clear cell sarcoma.