Case  1

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.



Differential diagnosis

  • Wilms\’ tumor
  • Neuroblastoma
  • Nephroblastomatosis
  • Multicystic dysplastic kidney
  • Renal cell carcinoma


  • Wilms瘤(肾母细胞瘤)
  • 神经母细胞瘤
  • 肾母细胞瘤病
  • 多囊性发育不良肾
  • 肾细胞癌

Diagnosis: Wilms\’ tumor


Discussion  讨论

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.


Key points

  • 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.


  • 肾母细胞瘤是儿童最常见的肾脏肿瘤,发病高峰年龄为3岁;
  • 肿瘤体积较大,可因体检或出现症状而发现;
  • 超声通常为首要检查,表现为肾脏较大的不均质肿物;
  • 可见肾静脉及下腔静脉受侵;
  • 肿瘤倾向于推移血管而不是包埋,借此可与神经母细胞瘤向鉴别。

Case  2

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.




Differential diagnosis

  • Clear-cell sarcoma
  • Wilms\’ tumor
  • Primitive neuroectodermal tumor
  • Renal cell carcinoma
  • Mesoblastic nephroma


  • 透明细胞肉瘤
  • 肾母细胞瘤
  • PNET
  • 肾细胞癌
  • 中胚层肾瘤


Diagnosis: Clear-cell sarcoma of the kidney (CCSK)



Key points

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).



Clinical presentation

Abdominal distention

Palpable abdominal mass

Rarer symptoms: vomiting and hypertension


  • 腹部膨胀
  • 可触及腹部肿物
  • 罕见症状:呕吐及高血压

Imaging features


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.




  • 肾脏肿物,体积较大,边界清楚;
  • 有不同程度的坏死、囊变;
  • 不均质强化;
  • 累及肾被膜外,相对较常见;
  • 少部分病例可见血管受累。



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