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Causes and pathogenesis of Wilms tumor
Last reviewed: 04.07.2025
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Wilms' tumor in 60% of cases is a consequence of somatic mutation, 40% of Wilms' tumors are caused by hereditary-determined mutations. Mutations of recessive suppressor genes WT1, WT2 and p53, located in chromosome 11, are of great importance in the pathogenesis of this tumor. According to Knudson's two-stage theory of carcinogenesis, the starting mechanism of Wilms' tumor can be considered a mutation in the germ cell, and then a change in the alternative gene in the homologous chromosome. In addition to idiopathic aberrations, Wilms tumor may be a manifestation of such hereditary syndromes as Beckwith-Wiedemann syndrome, WAGR (Wilms tumor, aniridia, genitourinary anomalies, and mental retardation), hemihypertrophy, Denys-Drash syndrome (intersex disorders, nephropathy, Wilms tumor), and Le-Fraumeni syndrome.
Wilms tumor pathology
The classic histological structure of Wilms' tumor is represented by three main components: blastomal, stromal and epithelial. The ratio of each of them in the tumor can vary significantly. Anaplastic changes are detected in 3-7% of tumors. Depending on the proportion of anaplastic cells in the tumor, focal (less than 10% of cells) and diffuse (more than 10% of cells) forms of anaplasia are distinguished. Diffuse anaplasia is associated with an extremely unfavorable prognosis.
Wilms tumor growth and metastasis
Wilms tumor is characterized by rapid locally invasive growth. In 6% of cases, Wilms tumor spreads through the lumen of the renal and inferior vena cava with the formation of tumor thrombi. Wilms tumor metastasizes by lymphogenous and hematogenous routes. Lymphogenous metastases affect regional retroperitoneal lymph nodes.
Further, the tumor may spread with the lymph flow along the thoracic duct upwards with the development of lesions of the supraclavicular lymph nodes on the left. The most common target for hematogenous metastasis is the lungs. Metastatic lesions of the liver, bones, skin, bladder, sigmoid colon, orbit, spinal cord, and contralateral kidney are also possible.
Wilms tumor classification
To determine the extent of the malignant process and standardize treatment approaches to nephroblastoma in children, most pediatric oncology clinics worldwide use the classification of the National Wilms Tumor Study Group.
National Wilms Tumor Research Group classification of nephroblastoma
Stage |
Tumor characteristics |
| I | The tumor is limited to the kidney and has been completely removed. The kidney capsule is intact, and the tumor integrity was not disturbed during removal. There is no residual tumor. |
| II | The tumor extends through the renal capsule but is completely removed. There may be some tumor in the lateral canal, or a tumor biopsy may be performed. Extrarenal vessels may contain tumor or may be infiltrated by tumor. |
| III | Residual non-hematogenous tumor in the abdominal cavity, lymph node involvement, dissemination through the peritoneum or tumor at the margin of the surgical incision, or tumor not completely removed |
| IV | Hematogenous metastases to the lungs, liver, bones, brain and other organs |
| V | Bilateral renal involvement at diagnosis |
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