Renal Tumors: Wilms Tumor (Nephroblastoma)

Fig. 62.1
Clinical photograph showing left-sided Wilms tumor
  • An abdominal swelling or mass
  • Abdominal pain
  • Fever
  • Nausea and vomiting
  • Hematuria
  • High blood pressure
  • The tumor can grow rapidly, which may result from bleeding into the tumor or from actual tumor growth.
  • Hematuria:
    • May be seen in 10–15 % of cases.
    • This is seen often after relatively minor trauma related to injury of an enlarged kidney involved by tumor.
    • Hematuria may be also a late presentation that is usually associated with tumor invasion of the calyces and is considered a bad prognostic sign.
  • Hypertension:
    • Increased blood pressure may be present in 20 % of cases.
    • Hypertension in Wilms’s tumor results from pressure effect of the tumor on the renal vessels leading to increased secretion of rennin.
  • Rarely, the tumor may produce erythropoietin leading to increased red blood cell production.
  • Wilms tumor can occur as part of rare genetic syndromes, including:
      1.
      Wilms tumor , aniridia , genitourinary anomalies, and mental retardation (WAGR) syndrome. This syndrome includes:
       
      • ◦ Wilms tumor
      • ◦ Aniridia
      • ◦ Abnormalities of the genitals and urinary system
      • ◦ Mental retardation
      2.
      Denys–Drash syndrome. This syndrome includes:
       
      • ◦ Wilms tumor
      • ◦ Kidney disease
      • ◦ Male pseudohermaphroditism
      • ◦ These patients mostly have bilateral or multiple tumors
      3.
      Beckwith–Wiedemann syndrome. This syndrome includes:
      • ◦ Omphalocele
      • ◦ A large tongue (macroglossia)
      • ◦ Enlarged internal organs
       

      Investigations

      • These include a complete blood count, blood urea nitrogen (BUN), creatinine, abdominal X-ray, abdominal ultrasound, computed tomography (CT) scan of the chest and abdomen, and magnetic resonance imaging (MRI; Figs. 62.2, 62.3, 62.4, and 62.5).
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        Fig. 62.2
        Abdominal (a) and chest (b) X-rays in a patient with left-sided Wilms tumor. Note the soft tissue density pushing the bowel to the right and secondaries in the chest
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        Fig. 62.3
        An intravenous urography in a patient with right-sided Wilms tumor (a). Note the mass displacing and compressing the remaining calyces downward. Abdominal ultrasound in a patient with a left-sided Wilms tumor (b)
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        Fig. 62.4
        Abdominal CT scan showing a large left-sided Wilms tumor. Note the thin rim of remaining kidney, which confirms that the tumor is arising from the kidney as opposed to neuroblastoma
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        Fig. 62.5
        Chest CT scan in a patient with Wilms tumor showing bilateral multiple secondaries (a) and abdominal CT scan showing bilateral Wilms tumor (b)
      • The aim is to evaluate the site, size, and extent of the tumor as well as the presence or absence of secondaries.
      • This as well as the function of the affected and contralateral kidney.
      • The presence or absence of synchronous tumors.
      • It is of great importance to exclude extension of the tumor into the renal vein as well as the inferior vena cava.
      • A plain abdominal radiograph often shows displacement of abdominal organs and occasionally the presence of calcification (< 10 %). The calcification usually is located on the edge of the tumor, whereas with a neuroblastoma, the calcification is speckled throughout.
      • Abdominal ultrasound confirms that the kidney is the site of the tumor, determines whether the mass is a cystic or solid tumor, and indicates if the tumor extends into the renal veins and inferior vena cava. Doppler ultrasound is a valuable investigation in detecting tumor extension in the renal vein and inferior vena cava.
      • CT scan defines the Wilms tumor site; identifies the presence of enlarged lymph nodes; evaluates the possible presence of a second Wilms tumor in the opposite kidney; assesses involvement of the tumor into the renal veins, inferior vena cava, and right atrium, and determines if the patient has intra-abdominal secondaries to the liver.
      • A chest CT is obtained to evaluate the presence of secondaries in the lungs.
      • Small abnormalities seen on chest X-ray are suggestive of secondaries, but those seen on CT scan may need to be confirmed by biopsy.
      • With the current radiological investigations, physical inspection of the opposite kidney by opening Gerota’s fascia as suggested previously to check for synchronous tumor is no longer necessary.

      Pathology

      • Grossly, Wilms tumor is a large, solitary, and well-circumscribed mass with the remaining rim of normal kidney tissue. There is usually a well-defined membrane between them. On cut section, Wilms tumor is soft, homogenous, and tan-gray in color and may contain areas of hemorrhage and necrosis (Fig. 62.6).
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        Fig. 62.6
        a Clinical photograph showing a resected large Wilms tumor arising from upper pole. Note the ureter and lower pole. b Clinical photograph showing a bisected Wilms tumor. Note the small normal renal tissue at the upper pole of the kidney
      • Pathologically, Wilms tumor is a malignant tumor composed of three elements (a triphasic nephroblastoma) .
      • These include metanephric blastema, mesenchymal stroma, and epithelium.
      • Characteristic of Wilms tumor is the presence of abortive tubules and glomeruli surrounded by a spindled cell stroma. The stroma may include striated muscle, cartilage, bone, fat, or fibrous tissue.
      • The mesenchymal component may also include cells showing rhabdomyoid differentiation. The rhabdomyoid component may itself show features of malignancy (rhabdomyosarcomatous Wilms). This particular subtype shows poor response to chemotherapy.
      • Pathologically, Wilms tumors are divided into two prognostic groups:
        1.
        Favorable: Contains well-developed components.
         
        2.
        Unfavorable (Anaplastic): Contains anaplastic cells, which could be focal or diffuse. This is associated with higher frequencies of relapse and death.
         
      • Most cases of Wilms tumor do not have mutations in any of the genes.
      • A gene on the X chromosome, WTX, is inactivated in up to 30 % of Wilms tumor cases.
      • The gene WT1:
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      Mar 8, 2017 | Posted by in PEDIATRICS | Comments Off on Renal Tumors: Wilms Tumor (Nephroblastoma)

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