What Are the Cancer Risks for BWS Genetic Subtypes?

When a child is diagnosed with Beckwith-Wiedemann syndrome (BWS), one of the first questions parents have is about the exact risk of childhood tumors. According to the 2018 International Consensus Statement, the overall likelihood of a tumor developing depends heavily on the child’s specific molecular subtype ^[1][2]. Overall cancer risks range from roughly 2.6% to 28%, depending on the underlying genetic cause ^[2][3].

The three primary childhood tumors associated with BWS are Wilms tumor (a type of kidney cancer), hepatoblastoma (a liver cancer), and neuroblastoma (a cancer of early nerve cells) ^[1]. These are called “embryonal tumors.” They arise from cells left over from fetal development, which is why the risk drops significantly after age 7 or 8—by that age, those susceptible cells have matured into normal tissue ^[1][2].

Tumor Risk Breakdown by Subtype

Here is a detailed breakdown of the consensus risk percentages for each major BWS subtype. These percentages reflect the likelihood of a tumor developing during early childhood ^[2][1].

Understanding these specific groups can help clarify your child’s exact risk profile:

• IC1-GoM (Gain of Methylation at Imprinting Center 1): Children with this subtype face the highest overall risk of developing tumors ^[1]. Their primary risk is Wilms tumor (about 24%) ^[2][3].
• pUPD11 (Paternal Uniparental Disomy of chromosome 11): This subtype carries an intermediate overall tumor risk of roughly 16% ^[4]. It is unique because children with pUPD11 have a statistically notable risk for both Wilms tumor (~7.9%) and hepatoblastoma (~3.5%) ^[2][5].
• CDKN1C Variants: Children with changes in this specific gene have a lower overall cancer risk (around 6.9%), but their risk profile is distinct ^[2]. They face an increased risk (about 2.8%) of neuroblastoma, while Wilms tumor and hepatoblastoma are virtually never observed ^[2][6].
• IC2-LoM (Loss of Methylation at Imprinting Center 2): This is the most common subtype of BWS and fortunately carries the lowest overall tumor risk, estimated at roughly 2.6% ^[2][3]. The primary slight risk here is for hepatoblastoma (about 0.7%), whereas Wilms tumor is extremely rare ^[2][7].

How Surveillance Uses These Numbers

These exact percentages guide the medical community’s recommendations for tumor surveillance—routine screening designed to catch tumors when they are small, localized, and highly treatable ^[1][3].

Here is what the 2018 International Consensus Statement recommends:

• Routine Abdominal Ultrasounds (For ALL Subtypes): Even though risks vary, the 2018 Consensus recommends that all children with BWS, regardless of their genetic subtype, receive a full abdominal ultrasound every 3 months until they reach age 7 ^[1][8]. This is because the overall risk for any BWS patient remains above the 1% threshold where medical screening is universally proven to be beneficial ^[1][9].
• Alpha-fetoprotein (AFP) Blood Tests: Hepatoblastoma screening with AFP blood draws is a complex topic. Because children with pUPD11 and IC2-LoM have varying risks of hepatoblastoma, some North American institutions recommend checking AFP levels every 3 months until age 4 ^[10][11]. However, European guidelines often advise against routine AFP testing because BWS patients naturally have fluctuating AFP levels that can lead to false alarms and unnecessary anxiety ^[1]. You will need to discuss with your specific medical team which approach they follow for your child’s subtype.
• Neuroblastoma Screening: While children with the CDKN1C variant have a 2.8% risk of neuroblastoma, the 2018 Consensus actually advises against routine urine tests (catecholamines) or specialized chest ultrasounds ^[1][3]. Studies show that these extra screenings do not improve survival outcomes but do cause a high rate of false positives ^[1]. Instead, doctors rely on physical exams and the standard 3-month abdominal ultrasounds to monitor for any changes.

It is crucial to remember that these percentages represent a statistical likelihood, not a certainty. For example, a 24% risk of Wilms tumor in IC1-GoM also means there is a 76% chance the child will never develop the tumor. The ultimate goal of knowing these exact numbers is not to induce fear, but to ensure your child is enrolled in a precise, evidence-based surveillance program ^[1].