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Renal (kidney) tumors occur when cancer cells form in the tissues of the kidney. There are different types of renal tumors in children. Together, they account for about 7% of all childhood cancers. Common types of pediatric kidney tumors include Wilms tumor (nephroblastoma) and renal cell carcinoma.
The kidneys are a pair of organs on either side of the spine in the back of the abdomen. Their main function is to filter and clean the blood and make urine.
Wilms tumor, also known as nephroblastoma, is the most common kidney cancer in children. About 500 children are diagnosed with Wilms tumor each year in the United States. It is most often found in children under 5 years of age. Among teens ages 15-19, the most common kidney tumor is renal cell carcinoma. Other kidney tumors include clear cell sarcoma of the kidney, malignant rhabdoid tumor, and mesoblastic nephromas. Other cancers such as sarcomas can occur in the kidney but may also arise in other parts of the body.
Common signs and symptoms of renal tumors include a lump, swelling or pain in the abdomen, blood in the urine, high blood pressure, fever, constipation, weight loss, or loss of appetite. Having certain genetic syndromes or other conditions may increase risk for developing a renal tumor.
Depending on the type of tumor, cancer may be found in one or both kidneys. Sometimes cancer may have spread to the lungs, liver, bones, brain, or lymph nodes at diagnosis.
Treatment for most renal tumors depends on the tumor and may include a combination of surgery, chemotherapy, and/or radiation therapy. Nephrectomy is surgery to remove all (radical nephrectomy) or part (partial nephrectomy) of the kidney. The type of renal tumor and extent of disease affects the prognosis and treatment options.
Common signs and symptoms of kidney tumors include:
Patients may have fatigue, confusion, excessive thirst, and/or vomiting due to high levels of calcium in their blood (hypercalcemia). Some patients may be treated for constipation without relief of symptoms due to the underlying abdominal mass.
Several types of tests are used to diagnose and evaluate kidney tumors. These tests include:
The stage of cancer indicates the size of the tumor and if the cancer has spread. Imaging tests, surgery, and pathology examination give information for the stage of disease. For all kidney tumor types:
For all renal tumors, patients with advanced stage disease (cancer has spread or metastasized to other parts of the body) have a poorer prognosis because the illness is more serious and harder to treat.
Wilms tumor (WT), also called nephroblastoma, is the most common type of kidney cancer among children. There are about 500 new cases in the United States each year. About 75% of patients diagnosed with Wilms tumor are under 5 years of age.
Wilms tumor may affect one or both kidneys. Children with Wilms tumor are usually diagnosed around 2-3 years of age if both kidneys are affected (bilateral) and 3-4 years of age if one kidney is affected (unilateral). 5-10% of patients have bilateral or multicentric disease (multiple tumors within the kidney) at diagnosis.
Common signs and symptoms of Wilms tumor include the following:
Patients may have fatigue, confusion, excessive thirst, and/or vomiting due to high levels of calcium in their blood (hypercalcemia). Some children may be treated for constipation for a few months before a diagnosis of Wilms tumors is made.
For most children with Wilms tumor, there is no clear cause. It affects males and females equally. Wilms tumor is more common in African American children compared to Caucasian children. It is less common in Asian populations. About 10% of patients with Wilms Tumor have inherited medical conditions or rare genetic syndromes that increase risk. These conditions include hemihyperplasia, aniridia, Denys-Drash syndrome, urinary tract abnormalities (WAGR syndrome), and overgrowth syndromes (Beckwith-Wiedemann syndrome).
In general, Wilms tumor is a curable disease. Five-year survival rates for Wilms tumor patients with favorable (less aggressive) histology are above 90%.
Prognosis depends on several factors. These include:
In the United States, patients with Wilms tumor usually undergo surgery to remove the kidney (nephrectomy) as soon as the cancer is found. If only one kidney is affected, the entire kidney is often removed. People can live normal, healthy lives with only one kidney.
Patients receive systemic combination chemotherapy after surgery.
Depending on surgery and histology results, treatment may also include radiation therapy.
Chemotherapy for Wilms Tumor with favorable histology most often involves two drugs: vincristine and dactinomycin for early stage disease (Stages I and II). For later stage disease (Stages III and IV), three drugs are commonly used: vincristine, dactinomycin, and doxorubicin. Additional medicines may be needed depending on tumor histology and response to treatment.
Surgery may not be possible at diagnosis for all Wilms tumor patients if the tumor is in both kidneys (bilateral) or is difficult to remove. Systemic chemotherapy is given to shrink the tumor, with surgery and radiation included later in the treatment plan. Nephron sparing surgery is a surgery method to remove the tumor while sparing healthy kidney tissue. This allows the patient to keep as much kidney function as possible. This is especially important in bilateral Wilms tumor to try to avoid possible kidney failure, dialysis and transplant. Nephron sparing surgery is performed after initial chemotherapy. It is important that the surgical team have experience in this procedure.
For children with a known risk for developing renal tumors, such as those with genetic predisposition due to family history or an inherited condition, regular screening for tumors is recommended. An abdominal ultrasound is usually performed every 3 months until 8 years of age. This helps with early diagnosis for patients at high risk.
Renal cell carcinoma (RCC) is very rare in children. Kidney tumors all together account for about 7% of childhood cancers. RCC accounts for only 5% of those kidney tumors. It is more common in adolescents ages 15-19 and is the most common kidney cancer among adults. Subtypes of RCC include translocation type, clear-cell, papillary, and unclassified. Compared to adults, children with renal cell carcinoma often present with more advanced disease at diagnosis (spread to lymph nodes). However, children tend to have better outcomes than adults, even with local lymph node involvement. If cancer has spread outside the kidney and lymph nodes to other sites such as the lungs or liver, then prognosis is poor.
Common signs and symptoms of RCC include:
Other symptoms may include high blood pressure, fever, loss of appetite, weight loss, and constipation.
Some inherited syndromes put children at higher risk for renal cell carcinoma. Conditions associated with RCC include von Hippel-Lindau disease, tuberous sclerosis, and other gene changes passed down in families. A subtype of renal cell carcinoma, renal medullary carcinoma, may be associated with sickle cell disease. Previous treatment for childhood cancers with radiation or chemotherapy is also a risk factor for renal tumors, including RCC.
Prognosis for patients with renal cell carcinoma depends on several factors:
Extent of disease greatly impacts prognosis. Five-year survival rates for pediatric RCC:
Surgery to remove the kidney and affected lymph nodes is the main treatment for renal cell carcinoma.
RCC does not respond well to radiation or chemotherapy, and there is no standard chemotherapy or radiation therapy used for this cancer. Small tumors may be treated with ablation to freeze or burn the cancer cells.
Immunotherapy may be used for people with advanced RCC.
Patients should have tumors tested for genetic factors such as translocations. Eligible patients may think about clinical trials that include targeted therapies, such as tyrosine kinase inhibitors, mTOR inhibitors, or ALK inhibitor therapy.
Rare childhood kidney tumors include:
Malignant rhabdoid tumors most often occur in young children and infants. This cancer can occur in other locations in the body as well as the kidney. Often, these tumors are not diagnosed until the disease is more advanced. Rhabdoid tumors of the kidney (RTK) can spread to the brain and lungs. Occasionally, rhabdoid tumors of the kidney occur together with atypical teratoid rhabdoid tumors (ATRT) in the CNS.
These tumors have a common genetic abnormality: a change in the SMARCB1 gene (also known as INI1, SNF5, and BAF47 gene). Less commonly, malignant rhabdoid tumor is caused by a mutation in the SMARCA4 gene. Children may have this mutation in every cell in their body (germline mutation). Patients with rhabdoid tumors should have testing for gene mutations and receive genetic counseling.
Unfavorable histology and anaplastic cells (cancer cells that divide rapidly and look very different from normal cells) are associated with lower survival rates. In rhabdoid tumor, older patients tend to have a better chance of recovery. The overall survival for children with malignant rhabdoid tumor is less than 50%. Children with metastatic disease have a very poor prognosis.
Malignant rhabdoid tumors (MRT) require surgery. A delay in surgery is associated with lower chance of survival. Although chemotherapy medicines can be used as a part of treatment, surgery is the central therapy. Researchers are studying multimodal therapy, including systemic chemotherapy with vincristine, cyclophosphamide, doxorubicin, carboplatin and etoposide. Targeted therapy is also under investigation through clinical trials.
Clear cell sarcoma of the kidney (CCSK) is very rare. This cancer represents less than 3% of pediatric kidney tumors. Only about 20 children are diagnosed with clear cell sarcoma in the United States each year. It is most often found in children ages 1-4 years, and it occurs more often in boys. Younger age and greater extent of disease at diagnosis are associated with less favorable outcome. Compared to other kidney tumors, CCSK is more likely to spread to bone. However, less than 5% of patients show metastases at initial diagnosis. Common sites for spread of disease include lung, bone, brain, and soft tissue.
Treatment of clear cell sarcoma of the kidney includes surgery to remove the kidney (nephrectomy). A CCSK diagnosis is made based on histology of the tumor. Multimodal therapy includes surgery, chemotherapy including doxorubin, and radiation after surgery. In the most recent Children’s Oncology Group study, children received combination chemotherapy with vincristine, doxorubicin, cyclophosphamide and etoposide with surgery and radiation.
Patients treated for clear cell sarcoma of the kidney are at risk for late recurrence. The most common sites for recurrence are the brain and lungs. Regular screening including imaging tests are part of follow-up care. Patients should also be monitored for kidney function and late effects of therapy.
Internal tandem duplications of the BCOR gene have been reported in clear cell sarcoma of the kidney (CCSK), but this gene abnormality is not associated with any genetic syndrome or clinical condition. Tumor genetics may allow for future treatment with targeted therapies.
Mesoblastic nephroma is a tumor that is usually seen in newborns and infants. The main symptom is the presence of a lump or mass in the abdomen. About 90% of patients are diagnosed within the first year of life. It is more common in boys. Sometimes a diagnosis is made before birth through prenatal ultrasound. Younger age (<3 months) is more favorable for patients with mesoblastic nephroma.
There are two major types of mesoblastic nephroma: classic and cellular. Classic mesoblastic nephroma is diagnosed prenatally or before 3 months of age. Cellular mesobalstic nephroma is associated with genetic translocation and has greater risk of recurrence.
Surgery to remove the kidney (nephrectomy) is the main treatment. In some cases, chemotherapy may also be used. Targeted therapies for tumors with genetic factors are being studied in clinical trials. The prognosis for mesoblastic nephroma is very good, and the survival rate is greater than 95%.
Patients will receive follow-up care to screen for recurrence for a period of time after treatment. The medical team will make specific recommendations for frequency and types of tests needed. Patients with certain inherited syndromes or genetic conditions may be at risk for future cancers and need additional care.
Patients who have had a kidney removed can lead normal, active lives with one kidney. However, it is important that families discuss medical needs and lifestyle habits with their doctor. Patients should have regular medical care with a check-up at least yearly. Tests should include blood pressure, kidney function (BUN, creatine), and urinalysis. If there are problems, patients should be followed by a nephrologist.
Children who receive treatment for kidney tumors are at risk for late effects related to therapy. For general health and disease prevention, all cancer survivors should adopt healthy lifestyle and eating habits, as well as continue to have regular physical checkups and screenings by a primary physician. Survivors treated with systemic chemotherapy or radiation should be monitored for acute and late effects of therapy. Serious chronic health conditions are present 25 years after diagnosis in approximately 25% of survivors, according to the Childhood Cancer Survivor Study. These conditions include second cancers (increased risk following exposure to radiation and certain chemotherapy drugs), congestive heart failure (exposure to doxorubicin), infertility or complications during pregnancy (increased risk following exposure to multiple different chemotherapy agents), and end-stage kidney disease or kidney failure. Survivors who had a nephrectomy are at higher risk for kidney problems.
Reviewed: June 2018