Pathways to Wilms' Tumor. Genetic changes leading to Wilms' Tumor. Cancer occurs through the sporadic or the syndromatic pathway. Loss of heterozygosity (LOH) and loss of imprinting (LOI) are generally associated with sporadic pathways, but are occasionally found in syndromatic tumors. The gray bar indicates that the LOH may occur anywhere along the development of the sporadic cancer. Most sporadic cases (but not all) have a wild-type overexpressed WT1 gene. It is possible that LOH, LOI, and other genetic changes in sporadic tumors compensate for the presence or over-expression of WT1. LOH at regions 16q and 1p correlate with poor prognosis. Other regions often showing LOH are listed. Regions 16p13.3, 17q25, and 4p16.3 are statistically enriched for predicted targets of WT1 but their involvement in tumor formation is unknown.