About

Wilms Tumor


About Wilms Tumors

Wilms tumors, also called Wilms’ tumor or nephroblastoma, typically occur in young children between 3 to 5 years old, and the incidence of these tumors decreases as kids grow older; Wilms tumors are very rare in adults. Each year, approximately 500 to 600 new cases of Wilms tumor are diagnosed in the United States, and an estimated 6% of all pediatric cancers are Wilms tumors.


Wilms tumor is a kind of childhood cancer that begins in the kidneys, and it accounts for about 9 of 10 kidney cancers in children. The majority of Wilms tumors are unilateral, meaning that only one kidney is affected. Usually, there is only one tumor in that kidney, but in a small number of cases there is more than one tumor in the same kidney. In about 5-10% of children with Wilms tumors, the cancer is bilateral, with tumors in both kidneys.

Generally, Wilms tumors grow rather large before they are detected. While the tumors are usually found before they metastasize (spread), they can spread to other organs – most often to the lungs and abdominal lymph nodes.

Most of the time, no known cause can be identified for Wilms tumor. However, there are some known risk factors, such as:

  • Age: the average age for Wilms tumors is about 3-4 years old.
  • Race/ethnicity: African-American children have a slightly higher risk than white children. The lowest incidence is among Asian-American children.
  • Gender: girls are slightly more at risk than boys
  • Family history: about 1-2% of children with Wilms tumor have one or more relatives with the same cancer.
  • Genetic syndromes: there is a strong association with certain kinds of hereditary syndromes (some of which are very rare). The syndromes linked to Wilms tumor include:
    • WAGR syndrome
    • Denys-Drash syndrome and Frasier syndrome
    • Beckwith-Wiedemann syndrome
    • Other syndromes are less strongly linked, such as Perlman syndrome, Sotos syndrome, Simpson-Golabi-Behmel syndrome, Bloom syndrome, Li-Fraumeni syndrome, and Trisomy 18
  • Birth defects: specific birth defects that are not associated with a genetic syndrome also put children at a higher risk of Wilms tumor, including aniridia, hemihypertrophy, cryptorchidism, and hypospadias.

Wilms tumors can grow very large before causing any symptoms, and children may act normally and look healthy during this time. Once symptoms present, the most common signs of Wilms tumor are:

  • Swelling or a large lump in the abdomen; may or may not be painful
  • Fever
  • Nausea
  • Loss of appetite
  • Shortness of breath
  • Constipation
  • Blood in the urine
  • High blood pressure

There are two major types of Wilms tumors, classified primarily by their histology, which is how they appear under a microscope.

  1. Favorable histology: the cancer cells don’t look normal, but the cells’ nuclei are not overly large or distorted. This type of Wilms tumor is much more common, and treatment generally leads to a favorable outcome.
  2. Anaplastic histology: the appearance of the cancer cells varies widely, and the nuclei are usually very large and distorted (called anaplasia). Diffuse anaplasia refers to when it is spread throughout the tumor, whereas focal anaplasia is when the distorted cells are limited to certain parts of the tumor.

In addition to these two classifications of Wilms tumor, the stage of the disease (how far it has spread) is also significant. According to guidelines from the Children’s Oncology Group (COG), Wilms tumor is staged as follows:

  • Stage I: about 20% of all cases; the tumor is located only in the kidney and can be entirely removed surgically.
  • Stage II: about 22% of all cases; the tumor spreads beyond the kidney but can be entirely removed surgically.
  • Stage III: about 32% of all cases; the tumor is limited to the abdomen but cannot be entirely removed surgically.
  • Stage IV: about 20% of all cases; the disease has spread into the bloodstream and may be found in other body organs, typically the liver or lung.
  • Stage V: about 6% of all cases; at diagnosis, the tumor is located on both kidneys (bilateral)

What are Wilms tumors?

Wilms tumor is a kind of childhood cancer that begins in the kidneys, and it accounts for about 9 of 10 kidney cancers in children. The majority of Wilms tumors are unilateral, meaning that only one kidney is affected. Usually, there is only one tumor in that kidney, but in a small number of cases there is more than one tumor in the same kidney. In about 5-10% of children with Wilms tumors, the cancer is bilateral, with tumors in both kidneys.

Generally, Wilms tumors grow rather large before they are detected. While the tumors are usually found before they metastasize (spread), they can spread to other organs – most often to the lungs and abdominal lymph nodes.

 

What are the risk factors of Wilms tumors?

Most of the time, no known cause can be identified for Wilms tumor. However, there are some known risk factors, such as:

  • Age: the average age for Wilms tumors is about 3-4 years old.
  • Race/ethnicity: African-American children have a slightly higher risk than white children. The lowest incidence is among Asian-American children.
  • Gender: girls are slightly more at risk than boys
  • Family history: about 1-2% of children with Wilms tumor have one or more relatives with the same cancer.
  • Genetic syndromes: there is a strong association with certain kinds of hereditary syndromes (some of which are very rare). The syndromes linked to Wilms tumor include:
    • WAGR syndrome
    • Denys-Drash syndrome and Frasier syndrome
    • Beckwith-Wiedemann syndrome
    • Other syndromes are less strongly linked, such as Perlman syndrome, Sotos syndrome, Simpson-Golabi-Behmel syndrome, Bloom syndrome, Li-Fraumeni syndrome, and Trisomy 18
  • Birth defects: specific birth defects that are not associated with a genetic syndrome also put children at a higher risk of Wilms tumor, including aniridia, hemihypertrophy, cryptorchidism, and hypospadias.

 

What are the symptoms of Wilms tumors?

Wilms tumors can grow very large before causing any symptoms, and children may act normally and look healthy during this time. Once symptoms present, the most common signs of Wilms tumor are:

  • Swelling or a large lump in the abdomen; may or may not be painful
  • Fever
  • Nausea
  • Loss of appetite
  • Shortness of breath
  • Constipation
  • Blood in the urine
  • High blood pressure

 

What many types of Wilms tumors are there?

There are two major types of Wilms tumors, classified primarily by their histology, which is how they appear under a microscope.

  1. Favorable histology: the cancer cells don’t look normal, but the cells’ nuclei are not overly large or distorted. This type of Wilms tumor is much more common, and treatment generally leads to a favorable outcome.
  2. Anaplastic histology: the appearance of the cancer cells varies widely, and the nuclei are usually very large and distorted (called anaplasia). Diffuse anaplasia refers to when it is spread throughout the tumor, whereas focal anaplasia is when the distorted cells are limited to certain parts of the tumor.

In addition to these two classifications of Wilms tumor, the stage of the disease (how far it has spread) is also significant. According to guidelines from the Children’s Oncology Group (COG), Wilms tumor is staged as follows:

  • Stage I: about 20% of all cases; the tumor is located only in the kidney and can be entirely removed surgically.
  • Stage II: about 22% of all cases; the tumor spreads beyond the kidney but can be entirely removed surgically.
  • Stage III: about 32% of all cases; the tumor is limited to the abdomen but cannot be entirely removed surgically.
  • Stage IV: about 20% of all cases; the disease has spread into the bloodstream and may be found in other body organs, typically the liver or lung.
  • Stage V: about 6% of all cases; at diagnosis, the tumor is located on both kidneys (bilateral).

 

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