History: A 2-year-old child presents with nausea and vomiting.
An abdominal radiograph is shown below.
Ultrasound images 超声图像
CT images CT图像
There is a mixed echogenic mass in the right kidney containing solid and cystic components. CT confirms a large mass centered at the lower pole of the right kidney.
- Wilms\’ tumor
- Multicystic dysplastic kidney
- Renal cell carcinoma
Diagnosis: Wilms\’ tumor
Wilms\’ tumor is the most common malignancy of the kidneys in children. The tumor can grow asymptomatically and is often identified on physical exam as an abdominal mass after significant growth. Children are usually identified with the tumor between ages 1 year and 5 years. Prognosis is very good with a cure rate of greater than 90%.
Radiologic overview 影像综述
Given that Wilms\’ affects the pediatric population, the initial imaging study is usually ultrasound. On ultrasound, Wilms\’ appears as a large, heterogeneous mass of the kidney. Wilms\’ often invades the renal vein and inferior vena cava (IVC), and there may be signs of tumor thrombus invasion on color Doppler.
After identification on ultrasound, chest CT is usually the next study to stage the tumor. The lungs are the most common location for metastasis. On CT, there is a large heterogeneous mass that replaces the kidney and displaces adjacent organs. There is no engulfment of vessels as seen with neuroblastoma and a “claw sign” is often seen as the tumor displaces the normal renal parenchyma. In 5% of cases, Wilms\’ involves the contralateral kidney, so special attention should be made in evaluating both kidneys.
In this case, there is a heterogenous mass involving the right kidney.
- Wilms\’ is the most common renal tumor in children. Peak age of incidence is 3 years.
- Wilms\’ can grow to a very large size before it is detectable on exam or is symptomatic.
- Ultrasound is the usual initial imaging test and will show a large, heterogenous mass arising from the kidney.
- There can be invasion of the renal vein and IVC.
- Wilms\’ tends to displace vessels rather than envelop them, which is what differentiates it from neuroblastoma.
History: A 28-month-old boy presents with a palpable lump in the left abdomen, first noticed one week prior.
Images from contrast-enhanced CT of the abdomen are shown below.
Axial and coronal contrast-enhanced CT images of the abdomen demonstrate a large well-circumscribed mass arising from the left renal medulla with mass effect upon and associated claw sign from the adjacent renal parenchyma. The mass demonstrates heterogeneous enhancement with large hypoattenuating components, corresponding areas of necrosis, and cystic change. The left adrenal gland is separately identified and normal in appearance. There is a hypodense left para-aortic lymph node, corresponding to nodal metastasis. No masses are seen in the contralateral kidney.
- Clear-cell sarcoma
- Wilms\’ tumor
- Primitive neuroectodermal tumor
- Renal cell carcinoma
- Mesoblastic nephroma
Diagnosis: Clear-cell sarcoma of the kidney (CCSK)
Clear-cell sarcoma of the kidney (CCSK)
Clear-cell sarcoma of the kidney is a rare, primary pediatric renal malignancy.
Classically associated with metastases to bone and brain:
Osseous metastases have been reported in 40% to 60% cases, which is much higher than the prevalence in Wilms\’ tumor (therefore, a useful feature to guide the differential diagnosis during initial evaluation).
Most prevalent location for metastases at presentation are lymph nodes (approximately 60%).
Clear-cell sarcomas of the kidney comprise approximately 5% of primary pediatric renal tumors.
It is the second most common pediatric renal tumor after Wilms\’ tumor.
Mean age of diagnosis is 36 months.
Rarely diagnosed at younger than 6 months of age.
There is a male gender predilection (approximately 2:1).
Palpable abdominal mass
Rarer symptoms: vomiting and hypertension
Clear-cell sarcoma of the kidney has a relatively nonspecific imaging appearance, often very similar to Wilms\’ tumor, so diagnosis needs confirmation with tissue histology.
Almost always a unilateral tumor (as opposed to Wilms\’ tumor, which can be bilateral).
Osseous metastases are more common in clear-cell sarcoma of the kidney than Wilms\’ tumor.
- CT demonstrates a large, well-circumscribed mass.
- There are variable proportions of necrotic and cystic components.
- Shows heterogeneous enhancement.
- Extracapsular extension is relatively common.
- Vascular involvement occurs in a small minority of cases.
Radionuclide bone scan: Useful for staging, given the relatively high frequency of bone metastases.