✅ Model Answer:
• Diagnosis: Wilms tumor (nephroblastoma).
• Evidence: Palpable abdominal mass, gross hematuria, hypertension (renin secretion), ultrasound showing a large renal mass.
• Next step: CT chest/abdomen (staging), surgical nephrectomy (if resectable), chemotherapy based on staging (NWTS/COG protocol). Preoperative: control hypertension (labetalol, amlodipine), avoid tumor rupture.

✅ Model Answer:
• WT1 gene: Chromosome 11p13 (tumor suppressor gene) – mutations in 10-15% of sporadic Wilms tumors.
• WT2 gene: Chromosome 11p15 (IGF2 imprinting) – associated with Beckwith-Wiedemann syndrome.
• Syndromes associated:
- WAGR syndrome: Wilms tumor + Aniridia + Genitourinary anomalies + Retardation (WT1 deletion).
- Denys-Drash syndrome: Wilms tumor + pseudohermaphroditism + nephropathy (WT1 mutation).
- Beckwith-Wiedemann syndrome: Wilms tumor + macroglossia + omphalocele + hemihypertrophy (WT2/IGF2).
- Frasier syndrome: Wilms tumor + gonadal dysgenesis (WT1 mutation).
• Inheritance: Sporadic (most) or autosomal dominant (syndromic).

✅ Model Answer:
• Classic triad (not always present):
- Palpable abdominal mass: Smooth, firm, non-tender (most common finding).
- Hematuria: Gross or microscopic (20-30%).
- Hypertension: Due to renin secretion (25-50%).
• Other features:
- Abdominal pain: Flank or generalized.
- Fever.
- Weight loss, failure to thrive.
- Microscopic hematuria: Incidental.
- Congenital anomalies: Aniridia, hemihypertrophy, genitourinary anomalies (in syndromic cases).
• Age: Most common between 1-5 years (peak at 3 years).

✅ Model Answer:
• Imaging:
- Abdominal ultrasound: First-line – shows a large, solid, hypoechoic renal mass.
- CT chest/abdomen: For staging – evaluates tumor size, involvement of renal vessels, lymph nodes, and lung metastases.
- MRI: If vascular involvement (renal vein/IVC thrombus).
• Laboratory:
- Urinalysis: Hematuria.
- Serum creatinine: To assess renal function.
- CBC: Anemia may be present (blood loss or marrow infiltration).
- Liver function tests: For metastatic evaluation.
- Urine catecholamines: To rule out neuroblastoma (if atypical).
• Genetic testing: If syndromic features (WT1, WT2).
• Biopsy: Usually not needed (diagnosis by imaging + nephrectomy). Preoperative biopsy if unresectable or suspected atypical (e.g., rhabdoid tumor).

✅ Model Answer:
• Staging (NWTS/COG):
- Stage I: Tumor confined to kidney, completely resected.
- Stage II: Tumor extends beyond kidney (perirenal fat, renal sinus) but completely resected.
- Stage III: Tumor not completely resected (lymph node involvement, spillage, residual disease).
- Stage IV: Hematogenous metastases (lung, liver, bone, brain).
- Stage V: Bilateral Wilms tumor.
• Treatment:
- Stage I-II (favorable histology): Nephrectomy + chemotherapy (vincristine + dactinomycin).
- Stage III-IV (favorable histology): Nephrectomy + chemotherapy (vincristine + dactinomycin + doxorubicin) + radiation (if stage III).
- Unfavorable histology (anaplastic): More intensive chemotherapy + radiation.
- Bilateral Wilms: Preoperative chemotherapy, then bilateral nephron-sparing surgery.
• Survival: >90% for favorable histology.

✅ Model Answer:
• Tumor-related:
- Tumor rupture: Preoperative or intraoperative – upstages to stage III.
- Renal vein/IVC thrombus: Can extend to the right atrium (requires surgical removal).
- Hypertension: May persist after nephrectomy (5-10%).
- Metastasis: Lung (most common), liver, bone, brain.
• Treatment-related:
- Chemotherapy toxicity: Myelosuppression, hepatotoxicity (dactinomycin), cardiotoxicity (doxorubicin – monitor echocardiograms).
- Radiation therapy: Risk of secondary malignancies (breast, bone), growth impairment, infertility.
- Renal function: Chronic kidney disease if bilateral or tumor recurrence.
- Second malignancies: Increased risk (especially after radiation).
• Other: Surgical complications (bleeding, infection, bowel obstruction).

✅ Model Answer:
• Prognosis:
- Excellent: Overall survival >90% with modern treatment.
- Favorable histology: Survival >95% for stage I; 80-90% for stage IV.
- Unfavorable histology (anaplastic): Survival 60-70%.
- Relapse: 10-15%; can be treated with salvage therapy.
- Long-term effects: Hypertension (5-10%), renal impairment (if bilateral or compromised), secondary malignancies.
• Long-term follow-up:
- Blood pressure monitoring: Annually.
- Renal function: Creatinine, eGFR, urine protein annually.
- Echocardiogram: If doxorubicin used (monitor for cardiomyopathy).
- Surveillance imaging: According to protocol (usually CT chest/abdomen every 3-6 months for 2-3 years).
- Genetic counseling: If syndromic.
- Education: Avoid NSAIDs, maintain healthy lifestyle.

✅ Model Answer:
• Wilms tumor (nephroblastoma):
- Origin: Renal embryonic tissue (nephrogenic blastema).
- Age: 1-5 years (peak 3 years).
- Location: Kidney (intrarenal).
- Presentation: Abdominal mass, hematuria, hypertension.
- Imaging: Large renal mass, displaces kidney.
- Biopsy: Triphasic histology (blastema, epithelium, stroma).
- Genetics: WT1, WT2.
- Treatment: Nephrectomy + chemotherapy (vincristine, actinomycin).
- Prognosis: >90% survival.
• Neuroblastoma:
- Origin: Neural crest (sympathetic nervous system).
- Age: <1 year (most common), can occur in older children.
- Location: Adrenal (40%), retroperitoneal, mediastinal.
- Presentation: Abdominal mass, fever, weight loss, opsoclonus-myoclonus, Horner syndrome.
- Imaging: Adrenal mass, may cross midline, calcifications.
- Biopsy: Small round blue cells, rosettes.
- Genetics: MYCN amplification (poor prognosis).
- Treatment: Surgery, chemotherapy, radiation, immunotherapy.
- Prognosis: Variable; good in infants (<1 year), poor if MYCN amplified.