Rhabdoid Tumor Predisposition Syndrome increases a person’s risk of developing a kind of rare, fast-growing tumor called a rhabdoid tumor. These tumors usually grow in the brain, spinal cord, and kidney. They may also develop in the ovary (also called “small cell carcinoma of the ovary, hypercalcemic type” or SCCOHT), soft tissues, lung, skin, and heart. These tumors are most common in children.
People with Rhabdoid Tumor Predisposition Syndrome are also at increased risk of developing non-cancerous tumors that grow in the nerves, called schwannomas. Schwannomas may cause painful lumps or tingling and numbness in some areas of the body. These tumors are more common in adults.
Not all people with rhabdoid tumors have Rhabdoid Tumor Predisposition Syndrome. When rhabdoid tumors develop in people without Rhabdoid Tumor Predisposition Syndrome, the tumors are called sporadic rhabdoid tumors. Only about 30–35% of people with rhabdoid tumors have Rhabdoid Tumor Predisposition Syndrome.
The majority of Rhabdoid Tumor Predisposition Syndrome cases are caused by changes in a gene called SMARCB1 (also called INI1). Genes carry information telling cells in the body how to work. The SMARCB1 gene helps to control how cells grow, divide, and die.
Most people without Rhabdoid Tumor Predisposition Syndrome carry two working copies of the SMARCB1 gene in their cells. One copy of SMARCB1 is inherited from each parent. Cells from people with Rhabdoid Tumor Predisposition Syndrome carry one working copy of SMARCB1 and one copy that is changed. This change causes the gene to not work properly. It is called a SMARCB1 variant.
A few children with Rhabdoid Tumor Predisposition Syndrome inherit their SMARCB1 variant from a parent who also has the syndrome. However, most children have a new SMARCB1 variant that did not come from a parent. These children have no history of the syndrome in their family. In these cases, the gene change either happened in an egg or sperm cell when the child was formed or in one of the child’s cells during pregnancy. These children are the first in their families to have Rhabdoid Tumor Predisposition Syndrome. No matter how they acquired the gene variant, people with Rhabdoid Tumor Predisposition Syndrome have a 50% (or 1 in 2) chance of passing it on to their children.
Most people born with one SMARCB1 variant are healthy at birth. As they get older, the second copy of the SMARCB1 gene might also become changed in one or more cells of the body. When this happens, those cells can develop into a tumor. This is why people with Rhabdoid Tumor Predisposition Syndrome have a greater risk of developing rhabdoid tumors and schwannomas.
Less commonly, Rhabdoid Tumor Predisposition Syndrome is caused by changes in a different gene called SMARCA4, particularly in people with SCCOHT.
A doctor may suspect this diagnosis after looking at a person’s medical or family history. In most cases, a doctor or genetic counselor will ask questions about the person’s health and the health of other family members. Read more about genetic counseling and genetic testing.
Diagnosing this syndrome is usually done by sequencing the SMARCB1 and SMARCA4 genes to find variants (gene changes). The testing is often done on tumor tissue when available and/or a blood sample.
People with Rhabdoid Tumor Predisposition Syndrome are at higher risk of developing rhabdoid tumors than are people in the general population. This risk is highest in childhood and decreases after age 5. Older children and adults with Rhabdoid Tumor Predisposition Syndrome are at increased risk to develop schwannomas. We are still learning about the tumor risks in older children and adults.
Although people with Rhabdoid Tumor Predisposition Syndrome are at higher risk for tumors, some people never develop them. Doctors do not yet understand why some people with Rhabdoid Tumor Predisposition Syndrome develop tumors and some do not. Further studies may help health care providers to better understand the risks.
Cancer screening involves tests to check for cancer before symptoms occur. The goal is to find cancer at the earliest and most treatable stage. Guidelines for cancer screening are available online. Recommended screenings may change over time as doctors learn more about this syndrome, so these screening tests should be discussed with a health care provider who knows this syndrome well.
Other ideas to reduce the risk of cancer include:
- Eat a healthful diet with lots of fruits and vegetables
- Get regular exercise
- Avoid smoking or using tobacco products
- Avoid secondhand smoke
- Avoid excess sun exposure and always wear sunscreen, hat, and protective clothing when out in the sun
- Get medical attention for unusual or ongoing symptoms
Resources about Rhabdoid Tumor Predisposition Syndrome:
- Children’s Brain Tumor Research Foundation (https://cbtf.org/)
- Young People with Cancer: A Parent’s Guide (www.cancer.gov/publications/patient-education/young-people)
Other resources:
- Making Sense of Your Genes: A Guide to Genetic Counseling (www.ncbi.nlm.nih.gov/books/NBK115508/)
Adapted from educational materials developed by the St. Jude Children’s Research Hospital Cancer Predisposition Program