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Imaging of Renal Neoplasms in Infants and Children

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  • 1. Imaging of Renal Neoplasms in Infants and Children Jason Coryell, MS4 March 31, 2006
  • 2. Guiding principles
    • Ultrasound is a standard first-line modality ; CT and MRI often are used to delineate extent of disease
    • Different tumor types share radiographic features; histologic diagnosis is the gold standard
    • Trends based on age, distribution of metastases, and appearance aid radiographic differentiation
    • Categorical approaches include age (infancy vs childhood), severity (benign vs malignant), and structure (solid vs cystic)
  • 3. Distribution by age
    • Infancy
      • Nephroblastomatosis
      • Mesoblastic nephroma
      • Wilms' (less frequent)
      • Rhabdoid
      • Ossifying renal tumor of infancy
    • Childhood
      • Wilms'
      • Clear cell sarcoma
      • Renal cell carcinoma
      • Multilocular cystic nephroma
      • Angiomyolipoma
      • Lymphoma (NHL)
      • Renal medullary carcinoma
      • Rhabdomyosarcoma (pelvis)
  • 4. Distribution by severity
    • Benign
      • Nephroblastomatosis
      • Mesoblastic nephroma
      • Multilocular cystic nephroma
      • Angiomyolipoma
      • Ossifying renal tumor of infancy
    • Malignant
      • Wilms'
      • Clear cell sarcoma
      • Renal cell carcinoma
      • Rhabdoid
      • Lymphoma
      • Renal medullary carcinoma
      • Rhabdomyosarcoma
  • 5. Wilms' tumor a) US demonstrates exophytic tumor of lower pole c) Contrast enhanced CT-well-circumscribed, lobulated, heterogeneously enhancing exophytic mass extending from superior pole of L kidney d) CT Coronal reconstruction in same patient e) MRI of same patient (Wilms' is variably hyperintense on T2 images)
  • 6. Epidemiology of Wilms' tumor
    • Account for 90% of pediatric renal tumors
    • Peak incidence = 3 years (<1-10)
    • Most often sporadic and unilateral
      • 1% familial (16% of familial cases are bilateral)
      • 10% bilateral (2/3 synchronus, 1/3 metachronus)
      • Increased risk for Wilms' with persistence of embryonic renal tissue (nephrogenic rests = nephroblastomas)
  • 7. Wilms' tumor associations
    • Molecular Associations-2 known tumor suppressor genes on chromosome 11
      • WT-1-assoc w/ WAGR (Wilms, aniridia, GU anomalies, retardation)
      • WT-2-loss of heterozygosity associated with Beckwith-Wiedemann
    • Associated conditions:
      • Beckwith-Wiedemann (omphalocele, gigantism, macroglossia)
      • hemihypertrophy,
      • Denys-Drash (pseudohermaphroditism, glomerulonephritis)
      • sporadic aniridia (1/3 develop Wilms')
      • Sotos (cerebral gigantism),
      • Bloom syndrome (facial telangiectasias, GI tumors)
      • Perlman syndrome (visceromegaly, gigantism, cryptorchidism)
    • Recommended US screening every 3-6 months for first 7 years; however, of uncertain benefit in overall survival
    • 15% of WT pts have other GU anomalies (cryptorchidism, horseshoe kidney)
  • 8. Wilms' tumor morphology
    • Large, spherical masses (avg 12 cm at dx) with pseudocapsule of compressed parenchyma
    • Heterogeneous density (hemorrhage, fat, necrosis, and/or calcification)
    • US is reliable for identifying tumor extension into renal vein or IVC (4-10% of cases)
    • CT or MRI to delineate tumor extent; tumor enhances to lesser extent than surrounding parenchyma
    • CXR or CT to identify pulmonary metastases
    Wilms' in L kidney of 4 year old with hepatic mets Tumor thrombus of portal v. in same patient
  • 9. Wilms' tumor staging
    • Stage I-confined to kidney without capsular or IVC involvement; completely resectable with capsule intact
    • Stage II-tumor extends beyond renal capsule or infiltrates vessels; resected tumor with confined local spillage
    • Stage III-residual tumor confined to abdomen, including positive abdominal nodes, positive surgical margins, diffuse peritoneal contamination, or residual nonresected tumor
    • Stage IV-hematogenous spread (lungs, nodes, liver)
    • Stage V-bilateral disease
  • 10. Don’t confuse Wilms' with neuroblastoma!!
    • Neuroblastoma-arises from anywhere along sympathetic chain or adrenal medulla
    • Most common cancer of infancy and most common extracranial solid tumor of childhood (90% dx <5 years; median age at dx 2 years)
    • 65% are intra-abdominal and they may invade renal tissue
    • Determining adrenal vs renal origin is difficult when there is no clear plane of separation
  • 11. Wilms' tumor vs Neuroblastoma
    • Wilms'
      • <10% are calcified; more often a curvilinear pattern
      • Occasional local para-aortic adenopathy (less common than with neuroblastoma)
      • IVC invasion has high positive predictive value
      • Mets to lungs common
    • Neuroblastoma
      • Often calcified; scattered pattern throughout mass
      • Large regional adenopathy
      • High predictive value: encasement of great vessels, spinal canal invasion, paravertebral mass
      • Moderate predictive value: extension across midline, displacement of great vessels
      • Mets to liver, bone common
      • Elevated urine catecholamines
  • 12. Which is it?
  • 13. Neuroblastoma This contrast-enhanced CT shows a large retroperitoneal mass adjacent to the left kidney with scattered hyperintense signal (calcification). The tumor encases the descending aorta.
  • 14. Wilms' tumor and neuroblastoma account for the majority of abdominal masses. The remainder of the slides will provide an overview of the less common renal neoplasms. They will be addressed in two groups: benign and malignant neoplasms
  • 15. Benign renal neoplasms
      • Nephroblastomatosis
      • Mesoblastic nephroma
      • Multilocular cystic nephroma
      • Angiomyolipoma
      • Ossifying renal tumor of infancy
    Hyperplastic perilobar nephroblastomatosis
  • 16. Nephroblastomatosis
    • Diffuse or multifocal kidney involvement of metanephric rests (embryonic renal tissue persisting beyond 36 weeks)
    • Homogenous subcapsular hypodense regions on contrast CT
    • Increased risk for Wilms' tumor. Present in:
      • 41% of unilateral casesof WT
      • 94% of metachronus WT
      • 99% of synchronus bilateral WT
    • Similar associations as with Wilms' Tumor (e.g. Beckwith-Wiedemann)
    • Treatment is controversial as 99% resolve spontaneously ; serial screening recommended with assoc. syndromes
    a) US of nephroblastomatosis (plus symbols) d) L kidney shows diffuse metanephric rests, while R kidney shows 3 focal lesions
  • 17. Mesoblastic nephroma
    • Most common renal neoplasm in 1 st three months
    • Solid, uniform mass with possible hypoechoic areas from cystic change or necrosis, thereby making it difficult to distinguish from Wilms' on US (or CT)
    • Has ill-defined margins and no capsule, thus needs wide surgical margins
    • Does not invade vascular pedicle or metastasize
    • US-large, solid mass with low echogenicity
    • CT-soft tissue attenuation; enhances less than surrounding parenchyma after contrast
    Prenatally diagnosed destructive renal mass; rim of capsule-like parenchyma; dx made after nephrectomy CT w/ contrast in same patient; rim of renal parenchyma ventromedially; well-defined mass surrounded by fat
  • 18. Multilocular cystic nephroma
    • Tumor contains cystic lesions lined by epithelial cells and fibrous septae (septae are only solid component of tumor)
    • Lining may contain blastema cells (cystic partially differentiated nephroblastoma), which may have malignant potential. This can only be discerned histologically.
    • Bimodal distribution ( boys < 4 years ; women 40-60 years)
    CT w/ contrast demonstrating cyst (arrow) within a cystic partially differentiated nephroblastoma
  • 19. Angiomyolipoma
    • Rare in children, unless pt has tuberous sclerosis
    • 80% of TS patients have renal angiomyolipomas by age 10 years
    • Hamartomatous lesions comprised of fat, smooth muscle, and blood vessels
    • In TS, small, bilateral, multifocal nodules, typically cortical
    • Tendency towards aneurysm formation with spontaneous bleeding in aneurysms >4 cm; treatment only indicated to manage hemorrhage
    • US-highly echogenic, non-shadowing foci correlating with fat content
    • CT w/contrast diagnostic if high fat content; otherwise, unenhanced may be necessary
    Acute hemorrhage of angiomyolipoma on contrast CT Selective digital subtraction angiography; increased irregular vascularity in area of angiomyolipoma (arrow); leaked contrast defines area of hemorrhage in pole
  • 20. Ossifying renal tumor of infancy
    • Rare tumor, diagnosed in 1 st year
    • Calcified renal hamartomas
    • Soft tissue mass arising from medulla, occupies part of collecting duct
    • Can cause sx of obstruction, hematuria
  • 21. Malignant renal neoplasms
      • Wilms'
      • Clear cell sarcoma
      • Renal cell carcinoma
      • Rhabdoid
      • Lymphoma
      • Renal medullary carcinoma
      • Rhabdomyosarcoma
    Gross examination of Wilms' tumor exhibiting extension into the renal pelvis
  • 22. Clear cell sarcoma
    • 4% of pediatric renal neoplasms
    • Age distribution similar to Wilms' tumor (peak 3-5 years)
    • No features that are radiologically distinct from WT (solid mass compressing, distorting surrounding parenchyma +/- cystic areas and necrosis
    • 20% have bony metastases (bone scan recommended)
    • Mets also to lung, brain, liver
    CT in 13 month old with right renal mass showing extensive central necrosis (arrow) and hydronephrosis of adjacent calices (arrowheads)
  • 23. Renal cell carcinoma
    • Mean age in children is 9 years
    • 1% of pediatric renal tumors
    • WT is 30 times more frequent in children overall; however, WT incidence is equal to RCC in 2 nd decade
    • More frequent with von Hippel-Lindau
    • Generally smaller than WT at presentation; otherwise radiographically indistinct from WT
    • 25% with calcifications (<10% in WT)
    • Lumbar aortic adenopathy common
    Coronal T1 MRI of renal cell carcinoma Gadolinium enhanced MRI
  • 24. Rhabdoid
    • 2-3% of pediatric renal neoplasms
    • Occur in 1 st year of life
    • High risk for synchronus or metachronus posterior fossa tumors (esp. PNET)
    • Radiographically indistinguishable from WT
    • Crescent sign- peripheral crescentic fluid in subcapsular or perinephric space on CT (not a high positive predictive value)
    • Renal vein infiltration common
    Gross appearance of rhabdoid-round, lobulated mass CT with contrast shows heterogeneously enhancing mass of L kidney
  • 25. Lymphoma
    • Non-Hodgkin’s lymphoma (esp. Burkitt’s) commonly has renal involvement
      • 8-12% seen on CT
      • 64% on autopsy
    • Usually bilateral dz--spread hematogenously or by direct extension
    • Common appearances:
      • Multiple parenchymal masses/nodules that distort the renal contour and displace the collecting system
      • Invasion from retroperitoneal mass or adjacent lymph nodes
    • CT-homogenous, hypodense on both enhanced and unehanced
    • Multifocal, nodular dz-may appear like multiple renal cysts
    • Diffuse dz-general renal enlargement
    • Associated splenomegaly, abdominal adenopathy , elevated LDH
    Gadolinium enhanced MRI of patient shows lymphomatous infiltration of the lower pole in both the coronal (b) and transverse (c) image; coronal also shows small focus in upper pole
  • 26. Renal medullary carcinoma
    • Aggressive tumor
      • Quickly fills renal pelvis
      • Invades vessels, lymphatics
      • Unfavorable prognosis
    • Most common in adolescents, young adults with sickle cell trait (SA, SC); no increased prevalence in SS disease
    • Centrally located, infiltrative lesion invading renal sinus
      • Peripheal caliectasis
      • Reniform enlargement
    • Adjacent adenopathy common
    US demonstrating lack of corticomedullary differentiation; hydronephrosis in calices CT with contrast shows heterogeneous, infiltrating mass (curved areas); hypodense areas reflecting hydronephrosis; extenseive paravertebral and para-aortic adenopathy (straight arrows)
  • 27. Rhabdomyosarcoma
    • Most common pediatric malignancy of the pelvis
    • GU tract is the 2 nd most common site after head & neck
    • MRI preferred over CT
    • MRI, CT both show excellent contrast enhancement
    • Solid mass of muscle density with areas of necrosis
    • Botyroid subtype accounts for 5% (grape-like, polypoid mass most common in vagina)
    Pelvic rhabdomyosarcoma
  • 28. Bibliography
    • Grainger & Allison’s Diagnostic Radiology: A Textbook of Medical Imaging, 4 th ed. Churchill Livingstone, 2001; pp. 1757-1762.
    • Golden CB, Feusner JH. Malignant abdominal masses in children: quick guide to evaluation and diagnosis. Pediatr Clin N Am , 2002; 49:1369-1392.
    • Lowe LH, Hernanz-Schulman M et al. Pediatric Renal Masses: Wilms Tumor and Beyond. RadioGraphics , 2000; 20: 1585-1603.
    • Owens CM, Dicks-Mireaux C et al. Role of Chest Computed Tomography at Diagnosis in the Management of Wilms’ Tumor: A Study by the United Kingdom Children’s Cancer Study Group. J Clin Onc , 2002; 20: 2768-2773.
    • Riccabona M. Imaging of Renal Tumours in Infancy and Childhood. Eur Radiol , 2003; 13:L116-L129.
    • Scott DJ, Wallace WHB, Hendry GMA. With Advances in Medical Imaging Can the Radiologist Reliably Diagnose Wilms’ Tumours? Clinical Radiology , 1999; 54:321-327.
    Images obtained from above sources as well as Google Images