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  • Updated 01.05.2021
  • Expires For CME 01.05.2024

Atypical teratoid/rhabdoid tumors

Introduction

Overview

Atypical teratoid/rhabdoid tumor (AT/RT) is a highly malignant brain tumor that typically affects young children. Once considered rapidly fatal, intensive multimodal treatment regimens have resulted in improved survival for some patients. The Children’s Oncology Group (COG) published the largest series of prospectively treated patients with atypical teratoid/rhabdoid tumor, demonstrating significantly improved survival for patients younger than 3 years of age compared to historical cohorts. Atypical teratoid/rhabdoid tumor is the first pediatric brain tumor for which a candidate tumor suppressor gene, SMARCB1, was identified. Gene expression profiling analysis suggests that there are 3 distinct molecular subtypes of atypical teratoid/rhabdoid tumor.

Key points

• Atypical teratoid/rhabdoid tumor is often fatal, but subsets of patients are long-term survivors after intensive multimodal therapy.

• A somatic mutation of the SMARCB1 gene is found in nearly all atypical teratoid/rhabdoid tumors, and an immune-histochemical stain for the gene product can help pathologists readily identify the tumor.

• Patients with germline mutations for the SMARCB1 gene often have disseminated or synchronous tumors, and their disease may behave more aggressively.

• AT/RT appears to contain 3 to 4 subgroups with distinct epigenomic, transcriptional, and clinic-pathologic features.

• Studies that incorporated targeted biological therapies to treat atypical teratoid/rhabdoid tumor are underway.

Historical note and terminology

Atypical teratoid/rhabdoid tumor of the central nervous system is a rare, highly malignant disease that occurs primarily in young children. The disease is often simply referred to as AT/RT. It was first identified by Rorke and colleagues as a unique tumor type in 1987 (29). Prior to that time, patients with atypical teratoid/rhabdoid tumor were often misdiagnosed as having medulloblastoma or other embryonal tumor. This is understandable as approximately two thirds of atypical teratoid/rhabdoid tumors have components that resemble medulloblastoma or other embryonal tumors (34). In addition to rhabdoid cells, atypical teratoid/rhabdoid tumors often contain malignant epithelial and mesenchymal components that further distinguish them from medulloblastoma or other embryonal tumors. Because it histologically resembles the rhabdoid tumor of the kidney, atypical teratoid/rhabdoid tumor was sometimes referred to as malignant rhabdoid tumor of the brain or central nervous system (15) before it was recognized as a distinct entity. The World Health Organization began classifying atypical teratoid/rhabdoid tumor an embryonal grade IV neoplasm in 1993 (25).

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