The
Wilms' tumor-
aniridia-genital anomalies-
mental retardation (
WAGR) syndrome is associated with an increased risk for developing
Wilms' tumor. A right
nephrectomy was performed following the diagnosis of
Wilms' tumor in a 2-year-old girl with
WAGR syndrome and chromosome 11, del 11p13. Pathologic examination revealed intralobar nephrogenic rests and a peripelvic multicystic mass, sharply delineated from the adjacent typical intralobar nephrogenic rests and renal parenchyma, which may represent a cystic
Wilms' tumor (cystic partially differentiated
nephroblastoma). We studied the expression of the H19 gene by in-situ hybridization performed on
paraffin sections of the kidney. H19 is an imprinted maternally-expressed gene that is not translated to
protein and functions as a regulatory
RNA molecule. It is tightly linked with the paternally-imprinted gene of
insulin-like growth factor 2. While IGF2 presumably plays a role in
tumorigenesis of
Wilms' tumor, H19 is not expressed in the majority of Wilms'
tumors. The expression of H19 in the intralobar nephrogenic rests was found to be prominent in the component of the blastema and markedly reduced with differentiation to tubular structures similar to the fetal kidney. The differential diagnosis of hyperplastic intralobar nephrogenic rests from a small
Wilms' tumor arising in intralobar nephrogenic rests is difficult. Complete understanding of the chain of molecular events occurring in the evolution of Wilms'
tumors may lead to the development of
tumor markers to be used on
paraffin sections and so help in the differential diagnosis of
hyperplasia versus malignant transformation.