General Information About Rhabdoid Tumors of the Kidney
Rhabdoid tumors are extremely aggressive malignancies that generally occur in infants and young children. The most common locations are the kidney (termed malignant rhabdoid tumor s or MRT) and central nervous system (CNS) (atypical teratoid/rhabdoid tumor), although rhabdoid tumors can also arise in most soft tissue sites. (Refer to the PDQ summary on Childhood Central Nervous System Atypical Teratoid/Rhabdoid Tumor Treatment for information on the treatment of central nervous system disease.) Relapses occur early (median time from diagnosis is 8 months).[1,2]
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(Refer to the Wilms tumor Clinical Features and Diagnostic and Staging Evaluation sections of this summary for more information about the clinical features and diagnostic evaluation of childhood kidney tumors.)
Approximately two-thirds of patients will present with advanced-stage disease. Bilateral cases have been reported. Rhabdoid tumors of the kidney tend to metastasize to the lungs and the brain. As many as 10% to 15% of patients with rhabdoid tumors of the kidney also have CNS lesions. The staging system used for rhabdoid tumor of the kidney is the same system used for Wilms tumor. (Refer to the Stage Information for Wilms Tumor section of this summary for more information.)
Histologically, the most distinctive features of rhabdoid tumors of the kidney are rather large cells with large vesicular nuclei, a prominent single nucleolus, and in some cells, the presence of globular eosinophilic cytoplasmic inclusions.
Genes Associated With Rhabdoid Tumors of the Kidney
Rhabdoid tumors in all anatomical locations have a common genetic abnormality-loss of function of the SMARCB1/INI1/SNF5/BAF47 gene located at chromosome 22q11.2. SMARCB1 encodes a component of the SWI/SNF (SWItch/Sucrose NonFermentable) chromatin remodeling complex that has an important role in controlling gene transcription.[5,6] Based on gene expression analysis in rhabdoid tumors, it is hypothesized that rhabdoid tumors arise in early progenitor cells during a critical developmental window in which loss of SMARCB1 directly results in repression of neural development, loss of cyclin-dependent kinase inhibition, and trithorax/polycomb dysregulation. Identical mutations may give rise to a brain or kidney tumor.