Wilms’ tumor most often affects children ages 3 to 4 and becomes much less common after age 5. This tumor most often occurs in just one kidney, though it can sometimes be found in both kidneys at the same time.
Improvements in the diagnosis and treatment of Wilms’ tumor have improved the prognosis for children with this disease.
Wilm’s tumor tends to be encapsulated and vascularized that do not cross the midline of the abdomen. In cases of metastasis it is usually to the lung. A rupture of Wilms’ tumor puts the patient at risk of hemorrhage and peritoneal dissemination of the tumor. In such cases, surgical intervention by a surgeon who is experienced in the removal of such a fragile tumor is imperative.
Pathologically, a triphasic nephroblastoma comprises three elements:
Wilms’ tumor is a malignant tumor containing metanephric blastema, stromal and epithelial derivatives. Characteristic is the presence of abortive tubules and glomeruli surrounded by a spindled cell stroma. The stroma may include striated muscle, cartilage, bone, fat tissue, fibrous tissue. The tumor is compressing the normal kidney parenchyma.
The mesenchymal component may include cells showing rhabdomyoid differentiation. The rhabdomyoid component may itself show features of malignancy.
Wilms’ tumors may be separated into 2 prognostic groups based on pathologic characteristics:
- Favorable - Contains well developed components mentioned above
- Anaplastic - Contains diffuse anaplasia (poorly developed cells)
Wilms tumor is thought to be caused by alterations of genes responsible for normal genitourinary development. Examples of common congenital anomalies associated with Wilms tumor are cryptorchidism, a double collecting system, horseshoe kidney, and hypospadias.
Environmental exposures, although considered, seem relatively unlikely to play a role.
The exact cause for the development of wilm’s tumor is not kown but it is clear that cancer begins when cells develop errors in their DNA. The errors allow the cells to grow and divide uncontrollably and to go on living when other cells would die. The accumulating cells form a tumor. In Wilms’ tumor, this process occurs in the kidney cells.
In a small number of cases, the errors in DNA that lead to Wilms’ tumor are passed from parents to children. In most cases, there is no known connection between parents and children that may lead to cancer. Instead, something happens in the child’s early development that causes DNA errors and leads to Wilms’ tumor.
Anomalies and Syndromes associated with Wilm’s Tumor
Wilms’ tumor occurs more frequently in children with certain abnormalities present at birth, including:
- Aniridia. In this condition the iris — the colored portion of the eye — forms only partially or not at all.
- Hemihypertrophy. A condition that occurs when one side of the body is noticeably larger than the other side.
- Undescended testicles. One or both testicles fail to descend into the scrotum (cryptorchidism).
- Hypospadias. The urinary (urethral) opening is not at the tip of the penis, but is on the underside.
Wilms’ tumor can occur as part of rare syndromes, including:
- WAGR syndrome. This syndrome includes Wilms’ tumor, aniridia, abnormalities of the genitals and urinary system, and mental retardation.
- Denys-Drash syndrome. This syndrome includes Wilms’ tumor, kidney disease and male pseudohermaphroditism, in which a boy is born with testicles but may exhibit female characteristics.
- Beckwith-Wiedemann syndrome. Symptoms of this syndrome include abdominal organs that protrude into the base of the umbilical cord, a large tongue (macroglossia) and enlarged internal organs.
History of Presentation
The most common manifestation of Wilms tumor is an asymptomatic abdominal mass; an abdominal mass occurs in 80% of children at presentation.
Abdominal pain or hematuria occurs in 25%.
Urinary tract infection and varicocele are less common findings than these.
Hypertension, gross hematuria, and fever are observed in 5-30% of patients.
A few patients with hemorrhage into their tumor may present with hypotension, anemia, and fever.
Rare patients with advanced disease may present with respiratory symptoms related to lung metastases.
Findings on Physical Examination
Examination often reveals a palpable abdominal mass.The abdominal mass should be carefully examined. Palpating a mass too vigorously could lead to the rupture of a large tumor into the peritoneal cavity.
Special attention should be payed on the features of those syndromes (WAGR syndrome and Beckwith-Wiedemann syndrome [BWS]) and anomalies associated with Wilms tumor (ie, aniridia, genitourinary malformations, and signs of overgrowth).
The first sign is normally a painless abdominal tumor that can be easily felt by the doctor. An Ultrasound, Computed Tomography, or MRI are done first. Once a kidney tumor is found, a surgical biopsy is done. A sample of tissue from the tumor is sent to a pathologist, who looks at it under a microscope to check for signs of cancer and the specific pathological features of the tumor.
If a child is diagnosed with this condition the parents are advised to avoid pushing on the child’s belly area, and use care during bathing and handling to avoid injury to the tumor site.
The first step in treatment is to stage the tumor. Staging helps to determine how far the cancer has spread and to plan for the best treatment.
Surgical removal of kidney tissue is called nephrectomy. The various types of nephrectomy include:
- Simple nephrectomy. In this surgery, the surgeon removes the entire kidney. The remaining kidney can increase its capacity and take over the entire job of filtering the blood.
- Partial nephrectomy. This involves removal of the tumor and part of the kidney tissue surrounding it. It’s usually performed when the other kidney is damaged or has already been removed.
- Radical nephrectomy. In this type of surgery, doctors remove the kidney and surrounding tissues, including the ureter and adrenal gland. Neighboring lymph nodes also may be removed.
Radiotherapy and chemotherapy will often be started after surgery, depending on the stage of the tumor.