Rhabdoid Tumor

What is Atypical Teratoid Rhabdoid Tumor?

This is a rapidly growing tumor formed in central nervous system, which is mainly found in the cerebellum of the brain or in the brain stem, though it can develop in any part of the brain. It is an extremely atypical clinical condition, only 1% to 2% childhood brain tumors cover Atypical Teratoid Rhabdoid Tumor.

rhabdoid tumor

In short form this disorder is denoted as AT/RT. Atypical Teratoid Rhabdoid Tumor is a vast collection of cancerous tumors, named rhabdoid tumors, which can arise exterior of the CNS or brain and most found in the renal system (kidney), hepatic system (liver) or auxiliary sites. In majority of the cases, it has been identified that AT/RT is related to a meticulous mutation in INI1 gene that can happen spontaneously or hereditary cause is involved.

Mostly children below 3 years of age are affected with AT/RT, but in rare cases, teenagers and adults can also affected with this disease. Previously, AT/RT was classified under medulloblastoma., but advancement of clinical science provide that information that AT/RT is a different type of malignant tumor, which need separate treatment approach.

Malignant Rhabdoid Tumor (MRT)  is an atypical childhood tumor that usually initiates in the kidneys. Furthermore can transpire in accompanying soft tissues or in the CNS (mainly in the brain). Then Malignant Rhabdoid Tumor is termed as where it is referred to as Atypical Teratoid Rhabdoid Tumor.

External Malignant Rhabdoid Tumor spread to the soft tissue of the associated site of the brain, mostly occupies  a deep axial location like the neck or paraspinal region. In addition, extrarenal rhabdoid tumors have been found in the brain, liver, chest, heart, tongue, neck, pelvis, extremities, and several other sites.

This is an extremely hostile, but rarely developed tumor. It arises at the early stage of life, therefore infant and children are affected in most cases. The external malignant rhabdoid tumor has specific characteristics, i.e. ‘rhabdoid cells’,  which are also present in definite soft-tissue sarcomas, like extraskeletal myxoid chondrosarcoma, synovial sarcoma, and leiomyosarcoma. ^{(1, 3, 4)}

Symptoms

AT/RT progresses exceptionally quickly and, as a consequence, symptoms can extend rapidly within days or weeks. General following symptoms of AT/RT occur, though this may vary with age of the affected child.

• Nausea and vomiting
• Exhaustion and tiredness
• Headache (particularly after wake up in the morning)
• Difficulty in body balancing and coordination
• Hydrocephalus (increased head size in infants)

In case of involvement of the kidney, Rhabdoid Tumor provides local clinical presentation and signs i.e. haematuria and flank/loin mass. ^{(1, 2)}

Diagnosis

Diagnostic measures for malignant rhabdoid tumor are used to find out the accurate category of tumor develops in child and also check the malignant nature of the tumor. After discussing the sign and symptoms, doctors usually go through the medical history and then perform the physical examination.

Physical examination includes checking of reflex action test for detecting the condition of neurologic function, strength of the muscle, movement of the eye and mouth, coordination and attentiveness.

In addition, the physician may recommend the following diagnostic tests for detecting the location of the tumor, underlying cause and malignant nature of the tumor:

• Magnetic resonance imaging (MRI) — to generate comprehensive images of expected organs and/ or structures within the body and/or vertebral column.
• Computerized tomography scan  (CT scan) — to get confine a complete analysis of the body, and confirm for other tumors in the chest, abdomen, chest and pelvis.
• Biopsy — a small tissue sample taken from the tumor to offer perfect sequences about the type of tumor.
• Lumbar puncture (also called an LP or spinal tap) —  take out a little sample of cerebrospinal fluid (CSF) and find out expansion of malignant cells. This procedure is usually completed by providing sedative for  the child.
• Ultrasound — To check the involvement of the kidney or other abdominal organ whole abdomen ultrasound is also performed.
• Genetic testing — The collected biopsy sample may also send for genetic testing to determine the abnormal mutation of the involved gene, as specific genetic defect is often related with AT/RT. The involved gene mutation is named as SMARCB1 (this gene also known as INI1, SNF5 and BAF47), which is usually responsible for all rhabdoid tumors.
• Germline mutation – this test is performed if the genetic test result is positive. In this test parental or familial genetic abnormality detects to find out the source of the abnormality and may also recommend genetic counseling. ^{(1, 2)}

Treatment

The possible treatment options are:

• Surgery is recommended depending upon the location of the tumor and the aim of the surgery is to remove possible involved part of the tumor.
• Radiation is added along with the surgical intervention, as it helps to kill the cancer cells, which is left behind after surgery. Depending upon the site of the tumor, radiation therapy is also applied to control the spreading of the local tumor.
• Chemotherapy involves medicinal agents that obstruct the cancer cell proliferation. Chemotherapeutic agents may use as a pre-adjuvant therapy of surgical process, as they assist to reduce the size of the tumor and provide the chance to complete removal of the tumor.
• If the tumor is located in the brain, then the intervention of intrathecal chemotherapy is frequently used as a significant factor of treatment, as it permits to deliver prescribed medicine straightway to the CNS to treat the tumor.
• Stem cell transplantor  bone marrow transplant is a novel therapy to treat with AT/RT, as in the bone marrow generates different types of blood cells. In AT/RT, bone marrow transplantation allows the body to take higher doses of chemotherapy. ^{(1, 2)}

References

1. Childhood AT/RT – Atypical Teratoid Rhabdoid Tumor; Retrieve from: http://www.dana-farber.org/health-library/childhood-at/rt—atypical-teratoid-rhabdoid-tumor.aspx

2. Malignant Rhabdoid Tumor in Children; Retrieve from: http://www.danafarberbostonchildrens.org/conditions/solid-tumors/malignant-rhabdoid-tumor.aspx

3. Oda Y, Tsuneyoshi M.; Extrarenal rhabdoid tumors of soft tissue: clinicopathological and molecular genetic review and distinction from other soft-tissue sarcomas with rhabdoid features; Pathol Int. 2006 Jun;56(6):287-95.; Retrieve from: http://www.ncbi.nlm.nih.gov/pubmed/16704491

4. Asif Abdullah, Yogesh Patel,Terrence J. Lewis, Haitham Elsamaloty, and Stephen Strobel  Extrarenal malignant rhabdoid tumors: radiologic findings with histopathologic correlation; Cancer Imaging. 2010; 10(1): 97–101.; Retrieve from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2842174/

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