Wilms' tumor overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Shanshan Cen, M.D. [2]
Overview
Wilms' tumor or nephroblastoma is a tumor of the kidneys that typically occurs in children, rarely in adults. It was first described by Dr. Osler in 1814. The tumour typically arises from mesodermal precursors of the renal parenchyma (metanephros). On microscopic histopathological analysis, tubules, solid sheets of small round cells, and stroma are characteristic findings of wilms' tumor. It may be caused by either genetic mutations or chromosomal alterations. The risk factors of wilms' tumor include family history, congenital anomalies, and associated syndromes. The complications of wilms' tumor include metastasis, high blood pressure, and kidney damage. Prognosis is generally good. The 5-year survival rate for Wilms tumor in children is around 90%, whereas older patients suffer worse outcome. The common symptoms include swelling, abdominal pain, fever, hypertension, and hypercalcemia. On abdominal examination a painless mass may be palpated in the flank. CT scan, MRI, Ultrasound, PET, and biopsy may be helpful in the diagnosis. The predominant therapy for wilms' tumor is surgical resection. Adjunctive chemotherapy and radiation may be required.
Historical Perspective
Wilm's Tumor was first discovered by Dr. Osler, in 1814.The association between Wilm's tumor 1 (WT1) and Wilm's tumor was made in 1990. Wilm's tumor is named after Dr. Max Wilms (1867-1918) who is a surgeon and pathologist from Germany. In 1969, the National Wilms Tumor Study (NWTS) group devised a therapy regimen for wilms tumor.
Pathophysiology
Wilms tumor has a triphasic appearance. It is comprised of 3 types of cells which are stromal, epithelial and blastemal. All the 3 types are not required for the diagnosis of wilms tumor. Primitive tubules and glomeruli are often seen comprised of neoplastic cells. Beckwith and Palmer reported in NWTS the different histopathologic types of wilms tumor to categorize them based on prognosis. Lesions comprising of nephrogenic rests can lead to wilms tumor. Wilms tumor (hereditary or sporadic) appears to result from changes in one or more of at least ten genes. Based on a study wilms tumor is divided into 2 pathologic categories: favorable and anaplastic. Wilms tumor (hereditary or sporadic) appears to result from changes in one or more of at least ten genes. The changes may be somatic or germline. Aberrations in germline or clonal WT1, WT2, and Wnt activation when combined with stage of development of the nephron, characterize different subsets of wilms tumor that can be differentiated by using gene expression profiling. This genetic/ontogenic categorization describes some of the heterogeneity among wilms tumors.
Causes
Wilms' tumor may be caused by either genetic mutations or chromosomal alterations.
Wilms' tumor differentiating from other disease
Wilms' tumor must be differentiated from neuroblastoma, cystic nephroma, and angiomyolipoma.
Epidemiology and Demographics
Wilms tumors are the most common pediatric renal mass. The incidence of Wilms tumor is estimated to be 0.71 cases per 10,00,000 children younger than 15 years. There is no significant gender predilection among unilateral cases, but the male to female ratio in bilateral cases is 0.60:1.00. It typically occurs in early childhood with peak incidence between 3 and 4 years of age. Asian individuals are less likely to develop wilms tumor.
Risk factors
Common risk factors in the development of wilms tumor include familial wilms tumor, congenital anomalies, WT-1 related syndromes and WT2-related syndromes. Less common risk factors in the development of wilms tumor include perlman syndrome, simpson-golabi-ehemel syndrome, Sotos syndrome, 9q22.3 microdeletion syndrome, Bloom syndrome, li-fraumeni syndrome and Alagille syndrome.
Screening
Screening can be very helpful to diagnose wilms tumor in high risk patients.Screening is done with serial abdominal ultrasonography.
Natural history, Complications and Prognosis
The symptoms of wilms tumor usually develop in the first decade of life, and start with symptoms such as an abdominal/flank mass. If left untreated, patients with wilms tumor may progress to develop hypertension, anemia, weight loss, renal failure and metastasis. The overall 5-year survival rate is approximately 63% for patients aged 10 to 16 years. Depending on various factors at the time of diagnosis, the prognosis may vary. These factors are histology of tumor, stage of tumor, genetic and molecular markers and age of the patient.
Staging
Staging of wilms tumor is done based upon the extent of tumor anatomically and not done on the basis of its genetics, histology or molecular markers. Extensive disease and worse prognosis is denoted by a higher stage. The staging systems that are currently used are National Wilms Tumor Study (NWTS) system and International Society of Pediatric Oncology (SIOP) system. Both these systems divide wilms tumor into 5 stages.
Diagnostic Study Of Choice
Histology of the biopsy sample taken during surgery is the gold standard for the diagnosis of wilms tumor. Most of the tumors of the kidney have a favorable histology(90%).If anaplastic changes(3-7%) are found then the outcome is poor. If a case of wilms tumor is suspected in North America, then nephrectomy is done immediately. Contralateral kidney is also explored to check for disease and lymph node biopsies done. If tumor spill occurs then whole abdomen radiotherapy has to be done.
History and Symptoms
Patients with wilms tumor may have a positive history of an asymptomatic abdominal mass, abdominal pain and urinary tract infection. Common symptoms of wilms tumor include abdominal tenderness and Hematuria. Less common symptoms of wilms tumor include Hypertension, Fever, respiratory symptoms, Anemia, Varicocele, and Hypercalcemia.
Physical Examination
Physical examination of patients with wilms tumor is usually remarkable for high blood pressure, fever, pallor, aniridia and a palpable abdominal mass.
Lab Findings
The lab studies conducted in patients suspected with wilms tumor are Complete blood count (CBC), coagulation studies, urinalysis, liver function test, serum creatinine, serum calcium and cytogenetics studies.
Electrocardiogram
There are no ECG findings specific to wilms tumor.
X Ray
Abdominal x-ray typically reveals a large soft tissue opacity displacing bowel. This finding is incidental and cannot be used as a diagnostic tool.
Echocardiography or Ultrasound
CT
CT scan may be helpful in the diagnosis of wilms' tumor.
MRI
MRI may be helpful in the diagnosis of wilms' tumor.
Ultrasound
Ultrasound may be helpful in the diagnosis of wilms' tumor.
Other Diagnostic Studies
18F-fluorodeoxyglucose (FDG)-positron emission tomography (PET)-CT and biopsy may be helpful in the diagnosis of wilms' tumor.
Medical therapy
The predominant therapy for wilms' tumor is surgical resection. Adjunctive chemotherapy and radiation may be required.
Surgery
Surgery is the mainstay of treatment for wilms' tumor.