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Does Wilms Tumor Cross The Midline?

Wilms tumor is a common renal cancer in young children. In most cases, the condition develops in children with no genetic alterations. But then again, there are some children who have congenital abnormalities associated with their ailment. There are several causes of Wilms tumor, and they can either be classified as syndromic or non-syndromic. The former basically represents cases where gene alterations are involved with the Wilms tumor 1 genes and Wilms tumor 2 genes. On the other hand, the non-syndromic causes of Wilms tumor are those without any association with any symptoms or genetic pathology of the condition. With that said, it is important to keep in mind that Wilms tumor often affects only one kidney, but in other instances, both kidneys may be affected.[1]

Does Wilms Tumor Cross The Midline?

Does Wilms Tumor Cross The Midline?

Most nephroblastoma is usually on one side of the body, i.e. found on one kidney – the right or left kidney. But then again, the tumor can also be found on both kidneys, but the chances are less, and only about 5-10 % of Wilms tumor cases have both kidneys involved. Wilms tumor barely crosses the midline, i.e. the imaginary line that divides our body into two equal halves. Even in children with Denys-Drash syndrome, where bilateral Wilms tumor is most common, tend to have encapsulated and vascularized tumors that don’t cross the abdomen midline.[1]

CT scan of Wilms tumor in some patients may not be as conclusive since they manifest unusual characteristics. For example, the nephroblastoma may exhibit signs of exophytic growth, calcification, large lymph nodes, and even crossing of the midline, which are not common in Wilms tumor. Wilms tumor is usually round and has smooth margins, and although it doesn’t normally cross the midline, there is a 20% probability that it may cross the midline.[4]

Features Of The Wilms Tumor

The Wilms tumor, or rather nephroblastoma is a tumor that is characterized by an abdominal mass. The swelling is usually on the kidneys, but since it grows very large, it can easily be seen on the child’s belly. The mass is usually non-tender, meaning it is solid and hard. The tumor is usually intrarenal, meaning that it originates from within the kidney. Specialists believe that the tumor usually begins to grow as early as when a child is a fetus, where some cells that should form into the kidney grow abnormally resulting in the malignant growth.

Wilms tumor usually displaces adjacent structures, since it spreads directly. Additionally, it is confined to the flank, and may also displace the urinary collecting system. The early sign of Wilms tumor is a smooth lump in the child’s abdomen, and progressive symptoms include; nausea, fever, blood in urine, stomach pain, loss of appetite and hypertension.[2] [3]

Who Is At Risk For Wilms Tumor?

We’ve established that Wilms tumor is a childhood renal cancer. Also, we know that it can be as a result of genetic abnormalities, whereby it may co-occur with other conditions such as WAGR syndrome and Denys-Drash syndrome. Other than that, Wilms tumor may occur in children without these genetic altercations as sporadic cancer.

There are other factors which increase the risk of nephroblastoma in kids. They include; sex where girls are more susceptible to the tumor than boys and children with African ancestry. For boys with cryptorchidism i.e. the failure of one or both testicles to descend into the scrotum, or hypospadias – boys with the urethra not located at the right place at the tip of the penis – have a higher risk of developing a nephroblastoma.[5]


Wilms tumor is considered a flank mass that is ballotable. It may or may not cross the midline, but in most cases, it does not cross the midline. The likelihood of crossing the midline stands at 20%. The prognosis of patients with nephroblastoma is quite good, with a 90% survival rate for at least 5 years. In terms of numbers, that means that 9 out of 10 children will survive cancer.


Also Read:

Pramod Kerkar, M.D., FFARCSI, DA
Pramod Kerkar, M.D., FFARCSI, DA
Written, Edited or Reviewed By: Pramod Kerkar, M.D., FFARCSI, DA Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:July 9, 2019

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