Early Childhood Atypical Teratoid/Rhabdoid Tumors

Abstract

Atypical teratoid rhabdoid tumor (AT/RT) is a highly malignant embryonal tumor of the central nervous system (CNS), which occurs sporadically or in the setting of a rhabdoid predisposition syndrome. A peak incidence of AT/RTs is found in children aged less than 3 years at diagnosis. In this age group ATRT occurs as frequently as medulloblastoma, the most common malignant pediatric CNS tumor.The characteristic morphological feature of AT/RT is the presence of rhabdoid tumor cells and varying amounts of small -undifferentiated PNET-like, mesenchymal, and/or epithelial differentiated tumor cells. The morphological and imaging similarities with supratentorial PNETs and medulloblastomas may result in misclassification. The vast majority of AT/RTs are characterized by alterations of the SMARCB1 (hSNF5/INI1) gene that encodes a ubiquitously expressed protein. Alterations of SMARCB1 lead to loss of nuclear protein expression, which can be detected by an immunohistochemical staining.Currently, no definitive guidelines for optimal treatment have been established. Most recent treatment strategies recommend maximal safe surgery followed by multimodal therapy, including intensive chemotherapy often augmented with intrathecal therapy with or without high-dose chemotherapy (HDC), and focal or craniospinal irradiation. With this approach prolonged survival can be achieved in a proportion of patients.