WILMS TUMOR

Wilms Tumor

Wilms Tumor

Introduction

Wilms' Tumor, also known as nephroblastoma, is an embryonic malignancy of the kidneys in children. It is one of the most common malignancies in children. The tumor, named after the physician Max Wilms, who discovered it, predominantly affects one kidney (unilateral Wilms's tumor); however, in a small number of cases it may affect both kidneys (bilateral Wilms's tumor).

The incidence of the tumor is 0.8 cases per 100,000 people per year. Children from African backgrounds are more likely than any other ethnic group to have the tumor. Girls also have a slightly higher risk of the tumor than boys, although the reasons for this are unknown. Wilms' tumor arises from the primitive embryonic renal tissue. It contains epithelial, stromal, and blastemal elements. If all these are intact in histological findings, without any anaplastic features (nuclear enlargement, abnormal mitoses), the prognosis for survival is good.

The tumor presents as a solid or cystic mass, which displaces the collecting renal system. The tumor may extend into the renal vein or, rarely, into the ureter and down to the bladder. It often spreads through the lymphatic and vascular system.

The etiology of the tumor is unknown. It often presents as a sporadic tumor; however, genetic abnormalities may occur. The transcription factor WT1 (Wilms's tumor 1, locus 11p13) may have an aberration in one of the alleles, leading to formation of Wilms's tumor. WT1 was originally identified as a tumor suppressor gene for Wilms's tumor. Transcription factor WT2 (Wilms's tumor 2 locus 11p 15.5), which comprises two imprinted domains IGF2 (human insulin-like growth factor 2 gene)/H19 gene and KIP2/LIT1 genes, can undergo maternal deletion or alterations associated with imprinting, and this may also lead to the development of the tumor. It may also occur in association with other genetic syndromes. These include Beckwith-Wiedemann syndrome and WAGR (Wilms's tumor, Aniridia, Genitourinary malformations, and mental retardation) syndrome. Other genetic aberrations include loss of heterozygosity at chromosomes 1p and 16q, which is associated with a significantly increased risk of relapse and mortality. Familial Wilms's tumor is also common.

Symptoms include an abdominal mass, with possible abdominal pain. Patients often present with hypertension resulting from increased plasma rennin levels from the dysfunctioning kidney; this is often treated with angiotensin-converting enzyme inhibitors.

The mean age at diagnosis for the tumor is 3.5 years for boys and 4 years for girls. Diagnosis is made using imaging techniques such as ultrasound to diagnose a renal or abdominal mass. Computed tomography scan of the abdomen helps detect metastases. Magnetic resonance imaging is useful for detecting thrombosis in veins, particularly the inferior vena cava and renal vein.

Current treatment for the disease is based on the stage and pathology of the tumor. Preoperative chemotherapy with vincristine, actinomycin D, and cyclophosphamide for children with nonmetastatic Wilms's tumor improves overall survival. However, patients with histological features of anaplasia or sarcomatous Wilms's tumors (e.g., malignant rhabdoid tumors and clear cell sarcomas) are less responsive to vincristine and actinomycin D. Preoperative chemotherapy is particularly useful for very large tumors, bilateral Wilms's ...