Rhabdoid tumor

Overview

A rhabdoid tumor is a rare and highly malignant tumor of childhood, first described in 1978. These tumors were initially considered an aggressive variant of Wilms' tumor of the kidney, however, with newer diagnostic techniques, these tumors are believed to represent a distinct entity. Since that time, there have been fewer than 50 cases reported, although it is likely that some cases previously identified as medulloblastoma or as primitive neuroectodermal tumors (PNET) are in fact rhabdoid tumors. These tumors occur in young children, mean age at diagnosis of 3.5 years, with a range of 2 to 13 years. There are no reported cases in adults. Rhabdoid tumors occur equally in males and females. The location can be supratentorial, intraventicular, and infratentorial.

Symptoms

seizures - can be the only presenting sign for supratentorial lesions hydrocephalus - enlargement of the skull and pressure on the brain raised intracranial pressure - the tumor blocks the normal flow of cerebrospinal fluid and the tumor causes increased production of fluid, resulting in headaches, morning vomiting, lethargy, and disturbances in walking enlarged head size or fontanels (the soft "spot" that occurs before the bones in the head become solid) in infants

Causes

Cytogenetic, fluorescence in situ hybridization (FISH), and loss-of-heterozygosity (LOH) studies have revealed that malignant rhabdoid tumors frequently contain deletions at chromosome locus 22q11.1. Positional cloning efforts revealed that this locus contains the SWI/SNF related, matrix-associated, actin-dependent regulator of chromatin, subfamily B, member 1 (SMARCB1) gene, also known as human sucrose nonfermenting gene number 5 (hSNF5), integrase interactor 1 (INI1) , or 47-Kd Brg1/Bam– associated factor (BAF47). SMARCB1 encodes a member of the human SWI/SNF complex.

Combined analyses including FISH, coding sequence analysis, high-density single nucleotide polymorphism–based oligonucleotide arrays, and multiplex ligation-dependent probe amplification enable the identification of biallelic, inactivating perturbations of SMARCB1 in nearly all malignant rhabdoid tumors, consistent with the 2-hit model of tumor formation. Thus, SMARCB1 is presumed to function as a classic tumor suppressor and the primary gene responsible for malignant rhabdoid tumor development.

Diagnosis

Diagnostic procedures for rhabdoid tumor may include: magnetic resonance imaging (MRI) - a diagnostic procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body. MRI provides greater anatomical detail than CT scan and can better distinguish between tumor, tumor-related swelling and normal tissue. magnetic resonance spectroscopy (MRS) - a test done along with MRI at specialized facilities that can detect the presence of particular organic compounds produced by the body's metabolism within sample tissue that can identify tissue as normal or tumor, and may be able to distinguish between glial tumors and tumors of neuronal origin

Treatment

Specific treatment for a rhabdoid tumor will be determined by your child's physician based on: your child's age, overall health, and medical history type, location, and size of the tumor extent of the disease your child's tolerance for specific medications, procedures, or therapies how your child's doctors expect the disease to progress your opinion or preference