Rhabdoid Tumor - Causes, Treatment & When to See a Doctor

What is Rhabdoid Tumor?

Rhabdoid tumor is a rare, highly aggressive cancer that most commonly arises in the kidneys (known as malignant rhabdoid tumor of the kidney, MRTK) or in the central nervous system (called atypical teratoid/rhabdoid tumor, AT/RT). The tumor is composed of cells that resemble rhabdomyoblasts—precursor muscle cells—hence the name “rhabdoid.” Although it can occur at any age, the majority of cases are diagnosed in infants and very young children, often before age 2. Because of its rapid growth and tendency to spread (metastasize) early, rhabdoid tumor carries a poorer prognosis than many other pediatric cancers.¹

Common Causes

Rhabdoid tumors are not caused by lifestyle factors or infections. Instead, they are driven by genetic alterations that disrupt normal cell‑cycle control. The most important cause is loss‑of‑function mutations or deletions of the SMARCB1 (also called INI1) gene, which encodes a core component of the SWI/SNF chromatin‑remodeling complex. When this gene is inactivated, cells lose the ability to regulate DNA transcription properly, leading to malignant transformation. Below are the main conditions and risk factors that are known to be linked with rhabdoid tumor development:

• Germ‑line SMARCB1 mutation: Inherited mutations predispose children to rhabdoid tumor and other malignancies (e.g., schwannomatosis).²
• Somatic SMARCB1 deletion or mutation: Acquired in the tumor tissue itself; accounts for most sporadic cases.
• Other SWI/SNF complex gene abnormalities: Rarely, mutations in SMARCA4 or ARID1A have been reported.
• Chromosomal abnormalities: Gains of chromosome 1q and losses of 22q (where SMARCB1 resides) are common.
• Familial cancer syndromes: Though uncommon, families with a history of rhabdoid tumor may have a hereditary cancer‑predisposition syndrome.
• Prenatal exposure to high‑dose radiation: Very limited evidence suggests a possible association, but data are inconclusive.
• Extremely low birth weight: Some epidemiologic studies have noted a modest increase in risk.
• Environmental mutagens: No specific agents have been definitively linked, but general carcinogen exposure may play a role.

Associated Symptoms

Because rhabdoid tumors grow quickly, they often cause a combination of local and systemic signs. The exact symptoms depend on the tumor’s primary site.

Kidney (MRTK)

• Abdominal swelling or a palpable mass, usually on one side.
• Blood in the urine (hematuria).
• Painful or difficult urination.
• Fever or unexplained weight loss.
• High blood pressure due to kidney involvement.

Central Nervous System (AT/RT)

• Persistent headache, often worse in the morning.
• Vomiting that is not related to food intake.
• Changes in vision or double vision.
• Weakness or paralysis on one side of the body.
• Seizures, especially in infants.
• Difficulty with balance or coordination.

Metastatic disease (spread to other organs)

• Shortness of breath or cough if the lungs are involved.
• Liver enlargement, jaundice, or abdominal pain.
• Bone pain or fractures when bone metastases occur.

When to See a Doctor

Early evaluation is critical. Seek medical attention promptly if you notice any of the following in a child (especially under 3 years old) or in yourself if a known rhabdoid tumor has been diagnosed:

• Sudden, painless swelling or a firm lump in the abdomen or flank.
• Unexplained persistent headaches, especially with vomiting.
• Unusual bruising, bleeding, or blood in the urine.
• Rapid weight loss or loss of appetite.
• New onset seizures or changes in level of consciousness.
• Persistent fever without a clear source.

Even if the symptom seems mild, if it is unexplained and occurs in an infant or young child, contact your pediatrician or go to the nearest emergency department.

Diagnosis

Diagnosing rhabdoid tumor involves a combination of imaging, tissue sampling, and molecular testing. The typical work‑up includes:

1. Physical examination and medical history

Doctors assess growth patterns, neurological status, and any family history of cancer.

2. Imaging studies

• Ultrasound: First‑line for suspected kidney masses; helps differentiate cystic from solid lesions.
• Computed Tomography (CT) scan: Provides detailed anatomy of the abdomen, chest, and pelvis; evaluates for metastases.
• Magnetic Resonance Imaging (MRI): Preferred for brain tumors (AT/RT) and for spinal involvement; offers superior soft‑tissue contrast.
• Positron Emission Tomography (PET) scan: May be used to stage disease and detect distant spread.

3. Laboratory tests

• Complete blood count (CBC) and metabolic panel.
• Urinalysis for hematuria.
• Serum lactate dehydrogenase (LDH) – often elevated in aggressive tumors.

4. Tissue biopsy

A core needle or surgical biopsy provides the definitive diagnosis. Pathologists look for characteristic “rhabdoid” cells—large, eosinophilic cytoplasm, eccentric nuclei, and inclusion‑like nucleoli.

5. Molecular and genetic testing

• Immunohistochemistry (IHC): Loss of INI1 (SMARCB1) protein staining is a hallmark.
• Fluorescence in situ hybridization (FISH) or PCR: Detect deletions or mutations in SMARCB1.
• Germ‑line testing: Recommended for families with a history of rhabdoid tumor or related cancers.

6. Staging

Staging follows the Children’s Oncology Group (COG) or the International Neuro‑Oncology Committee criteria, depending on tumor location. Staging determines whether disease is localized (Stage I‑II) or metastatic (Stage III‑IV).

Treatment Options

Management of rhabdoid tumor requires a multidisciplinary team that includes pediatric oncologists, surgeons, radiation oncologists, and supportive‑care specialists. Treatment is aggressive because of the tumor’s tendency to spread early.

1. Surgery

• Kidney tumors: Radical nephrectomy (removal of the affected kidney) is standard when feasible.
• Brain tumors: Maximal safe resection; complete removal is often limited by critical brain structures.
• In both cases, surgeons aim to achieve clear margins while preserving organ function.

2. Chemotherapy

High‑intensity, multi‑agent regimens are the backbone of treatment. Common protocols (adapted from COG studies) include:

• Vincristine
• Doxorubicin (Adriamycin)
• Cyclophosphamide
• Ifosfamide
• Etoposide
• Carboplatin
• Topotecan (often used for AT/RT)

Treatment cycles are repeated every 3‑4 weeks, with dose adjustments based on blood counts and organ function.

3. Radiation Therapy

Because rhabdoid tumors are radio‑sensitive, radiation is added for residual disease or metastatic sites. In infants, clinicians weigh the risk of long‑term growth‑plate damage against the benefit; newer techniques such as intensity‑modulated radiation therapy (IMRT) and proton therapy help spare healthy tissue.

4. Targeted and Emerging Therapies

• EZH2 inhibitors (e.g., tazemetostat): Show promise in early trials by targeting epigenetic dysregulation caused by SMARCB1 loss.
• CDK4/6 inhibitors: Under investigation for synergistic effect with chemotherapy.
• Immunotherapy: Checkpoint inhibitors have limited data but are being explored in combination regimens.

5. Supportive (Home) Care

While treatment occurs in a hospital, families can help the child’s recovery at home:

• Maintain a balanced, high‑calorie diet (often with nutritionist guidance) to counteract treatment‑related weight loss.
• Encourage gentle physical activity as tolerated to preserve muscle strength.
• Keep a medication diary to track chemotherapy side‑effects such as nausea, mouth sores, or fever.
• Practice strict hand‑washing and infection‑control measures; neutropenia is common.
• Utilize psychosocial resources—child life specialists, support groups, and counseling.

Prevention Tips

Because rhabdoid tumor is primarily driven by genetic mutations, most cases cannot be prevented through lifestyle changes. However, some strategies can reduce overall cancer risk and aid early detection:

• Genetic counseling: Families with a known SMARCB1 germ‑line mutation should receive counseling and consider early screening for at‑risk children.
• Prenatal care: Adequate folic acid intake and avoidance of known teratogens (e.g., high‑dose radiation, certain medications) support healthy development.
• Avoid unnecessary radiation exposure: Limit diagnostic X‑rays and CT scans in infants unless medically essential.
• Healthy environment: Reduce exposure to environmental pollutants and tobacco smoke, which are general cancer‑promoting factors.
• Regular pediatric visits: Routine physical examinations enable clinicians to spot abnormal abdominal masses or neurological signs early.

Emergency Warning Signs

Key Take‑aways

Rhabdoid tumor is a rare but extremely aggressive cancer that primarily affects infants and young children. It stems from loss of the SMARCB1 tumor‑suppressor gene, leading to rapid growth and early spread. Prompt recognition of symptoms—such as an abdominal mass, persistent headaches, or unexplained bleeding—followed by rapid imaging and biopsy, is essential for improving outcomes. Treatment is multimodal, combining surgery, intensive chemotherapy, radiation, and, increasingly, targeted agents. While prevention is limited, genetic counseling and vigilant pediatric monitoring are the best strategies for families at risk.

References:

1. Mayo Clinic. “Malignant rhabdoid tumor of the kidney.” Updated 2023. Link.
2. National Cancer Institute. “SMARCB1 (INI1)–Deficient Tumors.” 2022. Link.
3. Children's Oncology Group. “AT/RT Treatment Guidelines.” 2021. Link.
4. World Health Organization. “International Classification of Diseases for Oncology (ICD‑O).” 2020.
5. Cleveland Clinic. “Rhabdoid Tumor in Children.” 2023. Link.