Renal Mass
Robert Fleck, MD
DIFFERENTIAL DIAGNOSIS
Common
Wilms Tumor-Nephroblastoma
Nephroblastomatosis
Renal Cell Carcinoma
Mesoblastic Nephroma
Lymphoma
Less Common
Multilocular Cystic Renal Tumor
Abscess
Xanthogranulomatous Pyelonephritis
Clear Cell Sarcoma
Angiomyolipoma
Rare but Important
Rhabdoid Tumor
Renal Medullary Carcinoma
Ossifying Renal Tumor of Infancy
Metanephric Adenoma
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
DDx can be further limited by age, unique clinical or imaging features
Helpful Clues for Common Diagnoses
Wilms Tumor-Nephroblastoma
Most common (87%) of pediatric solid renal masses, bilateral in 10%
Age of presentation peaks at 3-4 years old; earlier peak for bilateral Wilms at 15 mo.
Associations: Cryptorchidism, sporadic aniridia, hypospadias, & hemihypertrophy
WAGR syndrome: Wilms, aniridia, GU anomalies, mental retardation
Drash syndrome: Male pseudohermaphroditism, glomerulonephritis
Beckwith-Wiedemann syndrome
Presents most commonly as palpable mass
Pain or hematuria are uncommon, hypertension in 1/4
Radiologically presents as large solid mass, often with vascular invasion
Spreads by direct extension; occasionally presents as cystic mass
Evaluate contralateral kidney for synchronous tumor or nephrogenic rests
Metastases most common to lungs (85%) and regional lymph nodes
Treatment (Tx): Nephrectomy followed by adjuvant chemotherapy
Presurgical treatment in bilateral disease with nephron-sparing surgery
90% 5-year survival rate
Nephroblastomatosis
Nephrogenic rests persisting to 36 weeks gestational age; rests seen in 1% of infants
Give rise to 30-40% of Wilms tumors
Found in 99% of bilateral Wilms tumors
CECT: Nephrogenic rests show relative ↓ enhancement to normal renal parenchyma
MR: Low signal intensity on T1 and T2
US: Hypoechoic compared with renal cortex, but US is less sensitive
Diffuse: Hypoechoic subcapsular layer
Nodular: Large hypoechoic masses
Natural history is regression but can transform to Wilms tumor
Syndromes associated with Wilms screened by US every 3 months to ˜ 7 years old
Renal Cell Carcinoma
Reported in ages 6 months to adulthood
7% of pediatric renal masses
> 10 years old: Diagnostic probability of renal cell vs. Wilms is equal
von Hippel-Lindau (VHL) syndrome
Often bilateral tumors
Presentation: Pain and hematuria
Metastases to lungs, bones, liver, or brain are frequent (20%) at diagnosis
More likely than Wilms tumor to be calcified (25% vs. 9%)
Tx: Radical nephrectomy and is resistant to chemotherapy
Mesoblastic Nephroma
a.k.a. fetal renal hamartoma and leiomyomatous hamartoma
Most common solid renal tumor in neonates
Majority present < 3 mo. as palpable mass
90% are diagnosed before 1 year of age
Large solid mass with ill-defined transition, no capsule, and usually involving renal sinuses
Local infiltration of perinephric tissue
Behavior is usually benign and cured by nephrectomy with wide resection of perinephric tissue to prevent recurrence
Rare metastasis to lungs, brain, or bones
Lymphoma
Involvement is common at autopsy
Only 3-8% show involvement at CT, mostly non-Hodgkin lymphoma
Primary involvement of kidney is rare
Symptoms do not occur until late stage
CT: Multiple hypoenhancing masses
US: Generally hypoechoic and can show increase through transmission
Helpful Clues for Less Common Diagnoses
Multilocular Cystic Renal Tumor
a.k.a. multilocular cystic nephroma
Cystic mass with scarce solid tissue
Age peaks of presentation: Up to 4 years old in boys or adult women
Appearance on imaging is multiple cysts
US is best at showing cystic nature
Multiple small cysts may give appearance of solid lesion on CT
Tx: Wide surgical resection; if recurrent, consider chemotherapy and radiation
Abscess
Predisposing factors: Reflux, urinary tract obstruction or anomalies, and diabetes
US: Complex mass with hypoechoic regions of liquefaction
Main differentiating features from other renal masses are fever, leukocytosis, and pyuria
Xanthogranulomatous Pyelonephritis
Diffuse type is unilateral with calcification and complex US appearance
Treatment is partial nephrectomy for focal type and nephrectomy for diffuse type
Clear Cell Sarcoma
a.k.a. bone metastasizing renal tumor
Peak incidence is 1-4 years old
Metastasizes to bones, lymph nodes, brain, liver, and lung
Tx: Nephrectomy and chemotherapy
Long-term survival approaches 70%
Angiomyolipoma
TS, neurofibromatosis type 1, and VHL syndrome
Lesions > 4 cm ↑ risk of hemorrhage
Fat on CT or MR is diagnostic
Helpful Clues for Rare Diagnoses
Rhabdoid Tumor
Rare aggressive tumor that histologically resembles tumor of skeletal muscle
Synchronous or metachronous brain tumors (especially posterior fossa)
Subcapsular fluid collections and tumor lobules differentiate from Wilms tumor
Renal Medullary Carcinoma
Adolescent with sickle cell trait or hemoglobin SC, not hemoglobin SS
Presents with gross hematuria and pain
Central, infiltrative causes caliectasis
Extremely aggressive with poor prognosis
Ossifying Renal Tumor of Infancy
Benign lesion, 8 of 11 cases reported in boys, 9 of 11 in left kidney
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