Nephroblastomas
Nephroblastomas, also known as Wilms' tumors, are the most common malignant kidney tumors found in early childhood, comprising about 6% of all childhood cancers. These tumors typically affect children aged six and younger, though they can occasionally occur in older children and adults. Nephroblastomas may arise sporadically or can be linked to congenital syndromes such as Beckwith-Wiedemann syndrome, WAGR syndrome, and Denys-Drash syndrome. Risk factors include genetic predispositions, with certain gene mutations contributing to tumor development, and a family history of nephroblastomas, with a noted higher incidence in Black Americans compared to other racial groups.
Symptoms often include a painless abdominal mass, which may be discovered incidentally, alongside other signs like abdominal pain, bloody urine, and fever. Diagnosis involves imaging techniques and surgical biopsy for confirmation. Treatment typically includes a combination of surgery, chemotherapy, and radiotherapy, depending on the tumor's stage. With advancements in treatment, particularly since the 1970s, the prognosis for nephroblastoma patients has improved significantly, boasting a five-year survival rate exceeding 90% for those with favorable histology.
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Subject Terms
Nephroblastomas
ALSO KNOWN AS: Wilms’ tumors
RELATED CONDITIONS: Beckwith-Wiedemann syndrome, WAGR syndrome (Wilms’ tumor-aniridia-genitourinary anomalies-developmental delays, Denys-Drash syndrome
DEFINITION: Nephroblastomas are the most common malignant kidney tumors of early childhood. Accounting for around 6 percent of all childhood cancers, nephroblastomas
Risk factors: Nephroblastomas may arise sporadically (in otherwise healthy children) or can be inherited. A nephroblastoma is sometimes linked to congenital disabilities such as aniridia (absence of the iris), hemihypertrophy (enlargement of one side of the body), and genitourinary abnormalities. Congenital disability syndromes associated with nephroblastoma include Beckwith-Wiedemann syndrome (tongue and internal organ enlargement and omphalocele), WAGR syndrome (Wilms’ tumor aniridia-genitourinary anomalies-developmental delays), and Denys-Drash syndrome (Wilms’ tumor, kidney disease, and ambiguous genitalia). Children aged six and younger are at highest risk, although older children and adults are occasionally affected. Black Americans appear to be at somewhat higher risk than White Americans and Asian Americans. Individuals with a family history of nephroblastomas are also at an increased risk.
Etiology and the disease process: There is compelling evidence that genetic mutations in up to ten different genes, most involving the tumor-suppressor genes WT1, WT2, or WTX, may be responsible for tumor development. As a result, primitive embryonic cells of the kidney fail to develop properly and instead multiply to form a tumor.
When tumor cells have a varied appearance and include large, misshapen nuclei, the tumor has anaplastic histology, which, when diffuse, may make treatment more difficult and lead to a poorer prognosis. Tumors with no anaplasia are said to have favorable histology. Most nephroblastomas have favorable histology.
Incidence: Annually, some five to six hundred children in the United States are diagnosed with nephroblastoma, with 10 percent of these cases forming part of a developmental defect syndrome. Most children are diagnosed at age three or four.
Symptoms: Most patients have a painless abdominal mass, usually an incidental finding by the doctor or the parent. Some complain of abdominal pain or swelling, bloody urine, nausea and vomiting, anorexia, weight loss, fever, and constipation. High blood pressure and low red blood cell levels are also common.
Screening and diagnosis: Lab tests, a thorough family medical history, diagnostic imaging ultrasound, chest X-ray, computed (CT) scan, and (MRI) will help determine the extent of tumor spread. Surgical tumor removal (resection) and tissue sampling will confirm the diagnosis. Tumor staging helps establish the treatment plan:
- Stage I: Tumor confined to the kidney, completely resectable
- Stage II: Tumor metastasis to local surrounding area, completely resectable
- Stage III: Tumor metastasis to surrounding area, not completely resectable
- Stage IV: Tumor metastasis to distant organs (e.g., lungs, liver, and brain)
- Stage V: Tumor present in both kidneys
Treatment and therapy: Treatment consists of a combination of surgery, chemotherapy, and radiotherapy. Nephrectomy (surgical removal of the kidney) can be partial, complete, or radical. Intravenous drugs, such as dactinomycin, doxorubicin, vincristine, and cyclophosphamide, are used for chemotherapy. Radiotherapy is usually confined to stage III, IV, and V nephroblastoma.
Prognosis, prevention, and outcomes: The NCI reports a good prognosis, with a five-year survival rate of over 90 percent for those with favorable histology. Outcomes for nephroblastoma patients have vastly improved since the 1970s, thanks to concerted efforts by the National Wilms’ Tumor Study Group (NWTSG) and the International Society of Pediatric Oncology (SIOP).
Bibliography
Estlin, Edward J., and Norbert Graf. "Renal Tumors." Pediatric Hematology and Oncology: Scientific Principles and Clinical Practice. Ed. Edward Estlin, Richard Gilbertson, and Rob F. Wynn. Wiley-Blackwell, 2010.
Vallance, Kelly L., and Jeffrey S. Dome. "Renal Tumors in Children." Renal Disease in Cancer Patients. Ed. Kevin W. Finkel and Scott C. Howard. Academic, 2014. 129–60.
"What’s New in Wilms Tumor Research?" American Cancer Society, www.cancer.org/cancer/types/wilms-tumor/about/research.html. Accessed 20 June 2024.
"Wilms Tumor." American Cancer Society, www.cancer.org/cancer/types/wilms-tumor.html. Accessed 20 June 2024.
"Wilms Tumor." Mayo Clinic, 4 May 2024, www.mayoclinic.org/diseases-conditions/wilms-tumor/symptoms-causes/syc-20352655. Accessed 20 June 2024.