Radiation Therapy in Atypical Teratoid/Rhabdoid Tumors

Abstract

The first description of primary malignant rhabdoid tumor was made by Beckwith and Palmer in 1978 as a highly malignant pediatric tumor of the kidney. Since then, this neoplasm appeared in many other parts of the body, including the central nervous system (CNS). The CNS variant of this tumor was recognized as the atypical teratoid rhabdoid tumor (AT/RT) when added as a separate entity to the World Health Organization (WHO) in 1993. AT/RT is a malignant embryonal tumor of the CNS that is composed of rhabdoid cells, with or without fields resembling classical primitive neuroectodermal tumor. Although the morphological pattern resembles other embryonal tumors of the CNS (medulloblastoma, PNET), it is shown to exhibit different serum marker expression and immunohistochemical (IHC) staining patterns from them and proved significantly more aggressive. To date, approximately 300 cases of AT/RT have been described in the literature. It is likely that the incidence of AT/RT has been underestimated given the clinical and histological similarities to medulloblastoma and the previous unavailability of IHC for routine diagnosis. Prior to recognition of AT/RT as a unique entity, many cases of AT/RT may have been misdiagnosed as medulloblastoma. Since the rise in accessibility of IHC testing in the late 1990s, the recognition of AT/RT has increased. Results from a pathologic review of a Children’s Cancer Group study of children with malignant brain tumors suggest that although AT/RT is a relatively rare disease, accounting for less than 5 % of all pediatric CNS tumors, up to 20 % of malignant CNS tumors diagnosed before the patient is 3 years old are AT/RTs.