Wilms tumor, also known as "nephroblastoma", is a solid tumor that arises from immature kidney cells. Wilms tumor is the fourth most common type of pediatric cancer, and is the most common type of kidney cancer to occur in children. Approximately 500 new cases are diagnosed each year. Wilms tumor most frequently occurs around the age of 3, and is rarely seen after 8 years of age. It usually affects only one kidney (unilateral), but in 5% of cases can affect both kidneys (bilateral). The overall five-year survival rate for children with Wilms' tumor is more than 90%. Prognosis depends on stage (how far the cancer has spread), histopathologic features (what the cancer cells look like under the microscope), patient age, and tumor size.
Most Wilms tumors are found only after the tumor has become quite large because the tumors can grow for some time without causing pain or making the child appear unhealthy. Luckily however, the tumors are usually discovered before they have metastasized (spread to other organs). Most commonly, the tumor is discovered because the child's abdomen begins to swell. Often parents appreciate a hard mass in the child's belly while they are bathing or dressing their child. The tumor is not usually painful to the child. Other less common symptoms of Wilms tumor include abdominal pain, fever, hematuria (blood in the urine), nausea, vomiting, weight change, change in bowel movements, or high blood pressure observed at the pediatrician's office (due to elevated levels of a substance in the blood called renin).
The child's physician will perform a physical examination, schedule imaging tests, and order laboratory tests to help determine if the child has Wilms tumor and to aid in developing the appropriate treatment plan.
Based on physical examination, imaging studies, laboratory tests, and possibly biopsy (tissue sample) the doctor will stage the tumor according to the following categories:
Stage 1: tumor confined to only the kidney and can be completely removed by surgery
Stage 2: tumor extends beyond the kidney but can be completely removed by surgery
Stage 3: cancer has spread slightly beyond the kidney (but not outside of the abdomen and pelvis) and can not be completely removed by surgery
Stage 4: cancer has spread outside the abdomen and pelvis to other organs such as the lungs, liver, bone, or brain
Stage 5: cancer in both kidneys
Age of the patient, size of the tumor, lymph node involvement and metastases at time of diagnosis, and appearance of the cancer cells are all important prognostic factors in determining survival.
Treatment of Wilms tumor involves combinations of surgery, chemotherapy, and possibly radiation. Due to advances in the treatment of Wilms tumor, the overall success rate in curing this type of cancer is now around 90%.
Surgical removal is the primary method for achieving local control of the cancer. A surgeon will perform a "nephrectomy" removing part of the kidney, the whole kidney, or the kidney plus surrounding tissue depending on the location and spread of the tumor at time of diagnosis.
Chemotherapy is a systemic treatment for Wilms tumor. Chemotherapy is taken orally or IV. It travels through the bloodstream and goes throughout the entire body to kill cancer that has spread beyond the kidney. Side effects of chemotherapy include nausea and vomiting, mouth sores, change in bowel habits, loss of hair, increased risk of infection, fatigue, and bruising.
Radiation uses high-energy rays to kill cancer cells. Radiation is used in the more advanced stages of Wilms tumor. Side effects of radiation include nausea, diarrhea, fatigue, and skin changes.
In a small number of cases, Wilms tumor arises as part of a congenital malformation syndrome. In the WAGR syndrome which results from a mutation at chromosome 11p, children have Wilms tumor, aniridia (absence of the iris of the eye), genital-urinary malformations, and mental retardation. In Denys-Drash Syndrome which also results from a mutation at 11p, children suffer from the combination of Wilms tumor, renal (kidney) disease, and pseudo-hermpahroditism ( genitalia are of one sex, but some physical characteristics of the other sex are present ). In Beckwith-Wiedemann Syndrome, children have macroglossia (a large tongue), omphalocele (abdominal organs outside of the body), Wilms tumor, and visceromegaly (large organs). Wilms tumor has also been described in association with Bloom Syndrome, Fanconi anemia, and Li Fraumeni syndrome.
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