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Wilms tumor
Last reviewed: 12.07.2025
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Wilms' tumor in children (embryonic nephroma, adenosarcoma, nephroblastoma) is a malignant tumor that develops from a pluripotent renal anlage - metanephrogenic blastema.
Wilms' tumor occurs with a frequency of 7-8 per 1 million children under 15 years of age, regardless of gender. Almost all kidney tumors in children are Wilms' tumors. In terms of occurrence in childhood, nephroblastoma ranks fourth among all tumors.
Pathological anatomy
Nephroblastoma is a solid tumor covered by a capsule. For a long time, the tumor grows expansively, without growing through the capsule or metastasizing. At the same time, it can acquire very large sizes, squeezing and displacing surrounding tissues. Small foci of fresh and old hemorrhages are detected in the thickness of the tumor tissue. Further development of tumor growth leads to capsule growth and metastasis.
Histologically, epithelial and storomal elements are revealed. Epithelial elements are represented by solid fields or strands of cells, in the center of which tubules are formed, resembling renal tubules. Between the solid fields there is loose fibrous tissue - stroma, in which various derivatives of the mesoderm can be found (striated and smooth muscle fibers, fatty tissue, cartilage, vessels, sometimes - derivatives of the ectoderm and neural plate).
In the world literature, several morphological variants of Wilms' tumor are distinguished, which are considered prognostically unfavorable and in 60% of cases cause a fatal outcome (in general, these signs are detected in 10% of nephroblastomas).
Anaplasia is a histological variant characterized by high variability in the size of cell nuclei with abnormal mitotic structures and hyperchromasia of enlarged nuclei. This variant occurs in children around 5 years of age.
Rhabdoid tumor - consists of cells with fibrous eosinophilic inclusions, but does not contain true striated muscle cells. Occurs in very young children.
Clear cell sarcoma - contains spindle-shaped cells with a vasocentric structure. Dominates in boys and often metastasizes to the bone and brain.
Metastasis occurs mainly to the lungs, as well as to the liver and lymph nodes.
Symptoms of Wilms Tumor in Children
Of the classic triad of signs of kidney tumors - hematuria, palpable tumor and abdominal pain syndrome - Wilms' tumor most often initially manifests itself as a palpable formation in the abdominal cavity. Pain and hematuria are detected later. In 60% of cases, arterial hypertension joins in over time. In addition, non-specific signs (fever, cachexia, etc.) may be observed.
The average age at diagnosis is 3 years. It should be taken into account that Wilms' tumor is often combined with congenital anomalies of the genitourinary system, sporadic aniridia and hemihypertrophy. Familial forms of Wilms' tumor are known, which are characterized by a high frequency of bilateral tumor lesions and more frequent congenital anomalies. If one of the parents is diagnosed with familial or bilateral Wilms' tumor, then the probability of its development in the child is about 30%.
Depending on the extent of tumor spread, there are 5 stages of the tumor process. At stage I, the process is limited to the kidney and the tumor usually does not grow through the capsule. The tumor can be removed without rupturing the capsule, and morphologically, no tumor tissue is detected along the edge of the specimen. At stage II, the tumor extends beyond the kidney and can be completely removed. Morphologically, tumor cells can be detected in the pararenal tissue. At stage III of tumor growth, non-hematogenous metastasis occurs within the abdominal cavity (periarterial and renal hilum lymph nodes; tumor implants on the peritoneum; the tumor grows through the peritoneal tissue; morphological examination reveals tumor cells along the edge of the specimen). At stage IV, hematogenous metastasis of the tumor to the lungs, bones, liver, and central nervous system is observed. At stage V, the tumor spreads to the second kidney.
Diagnosis of Wilms tumor in children
The detection of a palpable formation in the abdominal cavity, especially in combination with hematuria, requires the exclusion of nephroblastoma. In a small percentage of cases, the only manifestation of pathology may be hematuria. Ultrasound and excretory urography reveal intrarenal localization of the neoplasm, destruction of the renal collecting system. It is possible to detect calcifications at the site of old hemorrhages and signs of thrombosis of the inferior vena cava.
Differential diagnosis is carried out with other tumors, primarily with retroperitoneal neuroblastoma originating from the adrenal glands or paravertebral ganglia.
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Treatment of Wilms tumor in children
Complex treatment is carried out, including nephrectomy, polychemotherapy and radiotherapy.
Nephrectomy is performed immediately after diagnosis, even in the presence of metastases.
Treatment tactics largely depend on the stage of the disease. At stages I-III, nephrectomy is initially performed, while it is important to prevent rupture of the intact kidney capsule, since this significantly worsens the prognosis. At stages II-III, a course of radiation is administered in the postoperative period. At stages IV-V, preoperative irradiation of the tumor is possible according to individual indications.
Polychemotherapy is administered to all patients in the postoperative period. Wilms' tumor is quite sensitive to vincristine and actinomycin D, which are used in combination. In the most prognostically unfavorable cases, ifosfamide and anthracyclines are included in the therapy.
In the USA, the most widely used treatment protocol is the NWTS National Research Team; in European countries, the SIOR protocol has been developed. The effectiveness of therapy in each of them is approximately the same.
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Forecast
The prognosis is relatively favorable in children under 2 years of age at diagnosis and with a tumor mass of less than 250 g. Tumor recurrence and the presence of histologically unfavorable signs worsen the prognosis.
According to B.A. Kolygin (1997), the 20-year survival rate after complex therapy is 62.4%, and in recent years, with adequate implementation of the therapy protocol, the cure rate is 70-75% (8-year survival rate).
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