Nephroblastoma is a malignant embryonal tumor derived from the embryonic cells of the kidney. Nephroblastoma accounts for about 87% of all kidney tumors in children, with a peak age of 3 to 4 years and 80% of patients developing the disease before the age of 5 years. It is rare in the neonatal period. 4% to 13% of children have bilateral nephroblastoma. Nephroblastoma can be combined with other anomalies such as cryptorchidism, eccentric hypertrophy, hypospadias and sporadic aniridia. Several genetic mutations have been recently studied in association with the development of nephroblastoma, such as WT1, WT2, and P53. 1-2% of nephroblastomas have a family history, with familial cases having an early age of onset and a high incidence of bilateral cases. The tumor is mainly composed of epithelial cells, mesenchymal cells and germ cells; if one of the three main components reaches 65% or more, it is designated as germ type, epithelial type and mesenchymal type respectively; if all components do not reach 65%, it is designated as mixed type. The combination of mesenchymal changes in nephroblastoma, especially diffuse mesenchymal changes, is one of the indicators of poor prognosis. To determine the mesenchymal changes in tumor cells, three criteria must be present: 1) the diameter of tumor cells is at least three times larger than the adjacent cells of the same type; 2) chromatin is significantly increased; 3) multipolar nuclear division is present. However, the incidence of interstitial changes in nephroblastoma in children younger than 2 years old at the time of diagnosis is almost non-existent (its incidence is about 2%), and in children older than 5 years old the incidence of interstitial changes is about 13%. The most common symptoms are: abdominal mass (a smooth abdominal mass can be palpated during physical examination in more than 90% of children, mostly unintentionally), pain, hematuria, and systemic symptoms are rare, and hypertension is seen in 25% of patients due to renin production by the tumor. Diagnosis Imaging (ultrasound, enhanced CT): solid intrarenal mass with pseudo-envelope at the edge, and compression of renal parenchyma and collecting system. The tumor usually directly invades or pushes out surrounding structures, but rarely encases the aorta, a presentation that can help differentiate it from neuroblastoma. The tumor may invade the renal vein, inferior vena cava, or even the right atrium. Imaging requires attention to the renal vein, inferior vena cava, intrahepatic and peripheral lymph node metastases, contralateral concurrent tumors, and possible combined nephrogenic remnants. Chest CT: Lung is the most common site of distant metastasis for nephroblastoma, and chest CT scan should be done before surgery. IV. Stage 1: unilateral tumor, confined to the kidney, can be completely resected, with intact renal envelope, no rupture of envelope in nephrectomy, and no tumor residue; Stage 2: unilateral tumor spread outside the renal envelope, but can be completely resected, with tumor infiltration in the renal sinus or tumor embolus in the extrarenal vessels; Stage 3: non-hematogenous tumor residue, but confined to the abdomen: lymph node involvement, tumor overflow, rupture or puncture biopsy, tumor on the peritoneal surface implantation, residual tumor in the bulk or microscopically, or not completely resected; Stage 4: hematologic metastasis: lung, liver, bone, brain, etc.; Stage 5: bilateral nephroblastoma. Preoperative chemotherapy: Preoperative chemotherapy can reduce the chance of tumor rupture during surgery. Preoperative chemotherapy should be applied routinely in the following cases: bilateral nephroblastoma, tumors that cannot be removed by exploratory surgery, tumors that have spread to the hepatic vein and upper and lower vena cava. The duration of preoperative chemotherapy: 4-12 weeks; 3. Postoperative treatment: postoperative chemotherapy or radiotherapy plus chemotherapy needs to be decided according to the tumor stage and pathological type. The prognosis of tumor depends on the histological type and tumor stage, patient’s age and biological characteristics; most patients have good prognosis, and with systematic treatment, the 4-year survival rate of nephroblastoma reaches 90% regardless of the stage. For patients with diffuse mesenchymal lesions in stages 2-4, the 4-year recurrence-free survival rate is up to 54.8%.