Oncology · Pediatric Renal Tumors
The facts most likely to be tested
Wilms tumor is the most common primary renal neoplasm of childhood, typically presenting as an asymptomatic abdominal mass in a child younger than 5 years old.
The classic clinical presentation involves a firm, non-tender, smooth abdominal mass that does not cross the midline.
Patients often present with hematuria, hypertension due to renin secretion, and abdominal pain.
Wilms tumor is strongly associated with WAGR syndrome (Wilms tumor, Aniridia, Genitourinary anomalies, and intellectual disability) caused by a WT1 gene deletion on chromosome 11.
The initial diagnostic imaging modality of choice is an abdominal ultrasound, followed by a CT scan or MRI to evaluate for tumor extent and venous involvement.
The definitive management strategy involves surgical resection (radical nephrectomy) combined with adjuvant chemotherapy (typically vincristine and dactinomycin).
Wilms tumor must be distinguished from neuroblastoma, which typically presents as an irregular, crossing-the-midline mass associated with elevated urine catecholamines and systemic symptoms like fever or weight loss.
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A 3-year-old boy is brought to the clinic by his mother after she noticed a bulge in his abdomen while bathing him. Physical examination reveals a firm, smooth, non-tender mass in the left flank that does not cross the midline. The child is otherwise asymptomatic, but his blood pressure is found to be 115/75 mmHg, which is above the 95th percentile for his age. There is no evidence of lymphadenopathy or hepatosplenomegaly. Urinalysis is positive for microscopic hematuria.
What is the most likely diagnosis?
Wilms tumor (Nephroblastoma)
The presentation of a firm, non-midline-crossing abdominal mass in a young child, combined with hypertension and hematuria, is classic for Wilms tumor, as described in bets 1, 2, and 3.
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Etiology / Epidemiology
Most common renal malignancy in children; peak age 2-5 years. Associated with WAGR syndrome.
Clinical Manifestations
Painless, asymptomatic abdominal mass that does not cross the midline. Hematuria and hypertension.
Diagnosis
Initial imaging is abdominal ultrasound; definitive staging via CT abdomen/pelvis.
Treatment
Surgical nephrectomy followed by chemotherapy. Avoid palpating the abdomen to prevent rupture.
Prognosis
Excellent prognosis with 90% survival rate; monitor for congestive heart failure from anthracyclines.
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Epidemiology & Etiology
Peak incidence occurs between ages 2 and 5. It is strongly linked to genetic syndromes including WAGR (Wilms, Aniridia, Genitourinary anomalies, Retardation) and Denys-Drash syndrome. Most cases are sporadic, but familial cases show WT1 gene mutations.
Pertinent Anatomy
The tumor arises from the renal parenchyma, typically displacing the kidney. It is usually unilateral, though 5-10% of cases are bilateral. The mass is often firm and non-tender, occupying the flank.
Pathophysiology
The tumor originates from primitive metanephric blastema cells that fail to differentiate. It is a triphasic tumor consisting of blastemal, stromal, and epithelial elements. Rapid growth can lead to local invasion of the renal vein or inferior vena cava.
Clinical Manifestations
The classic presentation is a painless, firm abdominal mass discovered by parents during bathing. Patients may present with hematuria, abdominal pain, or hypertension due to renin secretion. Do not palpate the abdomen as this risks tumor rupture and peritoneal seeding.
Diagnosis
Initial evaluation requires abdominal ultrasound to confirm a renal origin. CT abdomen/pelvis with contrast is the gold standard for staging and assessing the contralateral kidney. A chest CT is mandatory to rule out pulmonary metastasis.
Treatment
Management involves radical nephrectomy combined with chemotherapy. Vincristine and dactinomycin are the standard first-line agents. Avoid aggressive palpation during physical exams. Radiation therapy is reserved for higher-stage disease.
Prognosis
The overall survival rate exceeds 90% with multimodal therapy. Long-term survivors require monitoring for secondary malignancies and cardiotoxicity from anthracycline-based chemotherapy.
Differential Diagnosis
Neuroblastoma: crosses the midline and causes systemic symptoms like fever/weight loss
Multicystic dysplastic kidney: usually presents as a non-functioning, cystic mass
Hydronephrosis: identified by fluid-filled renal pelvis on ultrasound
Polycystic kidney disease: typically bilateral and associated with family history
Renal cell carcinoma: significantly rarer in pediatric populations