Kidney tumors in children and adolescents

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What is the differential diagnosis of a child with an abdominal mass?

The most likely diagnoses in a child with an abdominal mass are neuroblastoma and Wilms tumor or nephroblastoma. Clinically, children with advanced stage neuroblastoma appear ill, often having signs or symptoms of metastatic disease such as periorbital ecchymoses or pain from skeletal lesions. Patients with Wilms tumor are often asymptomatic, and the mass may be discovered incidentally. Computer tomography (CT) scan of the abdomen can usually distinguish between the two cancers because neuroblastoma arises from the adrenal gland and compresses and displaces the kidney, whereas Wilms tumor is intrarenal and distorts the kidney.

2

What is the most common renal cancer in children?

Renal cancers represent about 7% of cancer diagnoses among children. Wilms tumor is by far the most common primary renal tumor in children younger than 15 years old, representing approximately 95% of diagnoses. In the United States, approximately 600 children are diagnosed with Wilms tumors each year. Renal cell carcinoma (RCC), the most common form of renal cancer in adults, represents only 2.5% of renal cancers in children younger than 15 years old, but in the 15- to 19-year age group, it surpasses Wilms tumor as the most common renal malignancy. Rhabdoid tumors and clear cell sarcoma of the kidney represent 1% and 1.6% of renal cancers, respectively.

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What are the most common sites for metastatic spread of renal tumors?

The most common sites of metastases in Wilms tumor are the lungs, regional lymph nodes, and liver. In patients with stage IV disease, the lungs are the only site of metastases in 80% of cases. Metastases to the liver, with or without lung metastases, are diagnosed in 15% of cases. Other sites of metastases in Wilms tumor are uncommon. Metastases to the brain can occur in rhabdoid tumors and clear cell sarcoma of the kidney. Bone lesions can be found in RCC.

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At what age is a child most commonly diagnosed with Wilms tumor?

Wilms tumor occurs most commonly in children between 1 and 5 years old, with a mean age at diagnosis of 3.2 years. Wilms tumor incidence is slightly higher in girls and in Black children than in other races in the United States.

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What is the typical clinical presentation of a child with Wilms tumor?

The most common presentation is an asymptomatic abdominal mass or swelling, often noted by a parent when bathing or dressing the child. Less common symptoms are fever, abdominal pain, gross or microscopic hematuria, and hypertension. Rarely, a child can present with an acute abdomen and uncontrolled bleeding because of tumor rupture. During the physical examination, special attention should be paid to signs of syndromes associated with Wilms tumor, such as aniridia, hemihypertrophy, and genitourinary anomalies.

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