Wilms Tumor

North American practice favors primary nephrectomy with lymph node sampling (≥5–6 nodes) for most Wilms tumors, reserving preoperative chemotherapy for IVC extension beyond infrahepatic level, respiratory compromise, or solitary kidney [e926-c1, e926-c2, e926-c23]. Tumors ≥13–15 cm warrant consideration of neoadjuvant therapy due to rupture risk . Core needle biopsy (≥10 cores) is mandatory when chemotherapy precedes resection, as imaging cannot distinguish histologic subtypes or anaplasia [e926-c4, e926-c5]. Stage 1–2 disease without metastases receives two-drug therapy (vincristine/dactinomycin) without abdominal radiation; stage 3–4 or metastatic disease escalates to three or more agents [e926-c10, e926-c12]. Loss of heterozygosity at 1p/16q (5–7% of cases) mandates treatment intensification regardless of stage [e926-c32, e926-c33]. Very low-risk patients (<2 years, <550 g, stage 1 favorable histology) may avoid chemotherapy entirely with >95% survival . Bilateral tumors (8–10% of cases) receive neoadjuvant VAD to enable nephron-sparing surgery on at least one kidney; biopsy is unnecessary in typical presentations but recommended for atypical cases (older age, syndromes) [e926-c36, e926-c37, e926-c39, e926-c41]. IVC thrombus below hepatic veins can be resected primarily; suprahepatic extension requires preoperative chemotherapy and may necessitate vascular isolation [e926-c28, e926-c29, e9086-c8]. Late effects—renal failure, second malignancies (15% breast cancer after chest radiation), cardiac disease, hypertension—drive ongoing de-escalation efforts [e926-c11, e926-c14, e10159-c10, e10159-c12].