Encyclopedia of Health and Medicine

232 The Urinary System
• decreased APPETITE and weight loss
• NAUSEA and VOMITING
• abdominal discomfort or PAIN
• generalized irritability and crankiness
The diagnostic path begins with a comprehensive
physical examination, BLOOD tests, and urinalysis.
Diagnostic imaging procedures such as
ULTRASOUND, COMPUTED TOMOGRAPHY (CT) SCAN, or
MAGNETIC RESONANCE IMAGING (MRI) can identify the
presence, size, and location of the tumor. Biopsy of
the tumor is necessary to confirm the diagnosis.
Microscopic examination of the biopsied tissue
further allows the pathologist to determine
whether the tumor’s cells are anaplastic, which
means they are highly irregular and divide both
rapidly and erratically. Tumors of anaplastic cells
may be diffuse through the kidney and are more
difficult to treat than tumors of what pathologists
call favorable cells (cancerous cells that are more
pathologically normal). The pathologist also
assigns the cancer a grade that identifies the
extent to which the tumor has spread (metastasized),
which helps determine the appropriate
treatment options.
Treatment Options and Outlook
NEPHRECTOMY (surgery to remove the affected kidney)
in combination with CHEMOTHERAPY is the
standard treatment for Wilms’s tumor cancers.
Partial nephrectomy removes the tumor and a
margin of kidney tissue around it; simple nephrectomy
removes the entire kidney. Radical nephrectomy
removes the kidney. The oncologist may also
add RADIATION THERAPY when the cancer’s stage is
advanced or its cells are anaplastic regardless of
stage.
When the tumor is very large or the cancer
involves both KIDNEYS, the oncologist may recommend
chemotherapy or radiation therapy (or a
combination of both) before surgery to shrink the
tumors as much as possible. The oncologist may
suggest participation in a clinical trial for inoperable,
stage 5, or recurrent Wilms’s tumor.
Treatment success largely correlates to the stage
of the Wilms’s tumor (the size of the tumor and
the extent to which it has metastasized) and the
characteristics of the cancer cells (anaplastic or
favorable) at the time of diagnosis. Wilms’s tumor
is among the childhood cancers doctors consider
curable.
Risk Factors and Preventive Measures
Researchers have recently identified GENE mutations
that account about 30 percent of Wilms’s
tumor cancers. Located on CHROMOSOME 11, these
are the Wilms’s tumor 1 (WT1) and 2 (WT2) genes
and provide encoding for development of urinary
and genital structures. Wilms’s tumor also is associated
with several rare genetic syndromes, making
it likely that other gene mutations further
contribute to the errant encoding that allows these
primitive cells to thrive. Family history raises the
risk for Wilms’s tumor, as it appears the gene
mutations are sometimes hereditary.
Researchers believe Wilms’s tumor represents
clusters of cells in the kidneys that remain primitive,
a consequence of the WT1 and WT2 mutations.
When these primitive cells divide, they
continue to do so at the same rapid rate of cell
division that was normal in the EMBRYO. In the
older child’s body, however, this is inappropriate
and the cells grow out of control, some wildly (the
anaplastic cells). Some researchers believe the cell
growth continues from early developmental stages
and ultimately manifests as a tumor when the
cluster of cells achieves enough mass. Other
researchers believe environmental factors, perhaps
processes in the body related to growth, trigger
the cells to resume dividing.
There are no measures to prevent Wilms’s
tumor. Families who have had children with
Wilms’s tumor should have any other children
undergo regular routine medical examinations
that include screening (such as ultrasound) for the
cancer. Doctors do not yet know the long-term
health implications for Wilms’s tumor survivors as
the treatments that make survival possible have
not been available long enough for many survivors
to have yet reached adulthood.
See also BLADDER CANCER; CANCER TREATMENT
OPTIONS AND DECISIONS; MUTATION; RENAL CANCER; SUR-
GERY BENEFIT AND RISK ASSESSMENT.