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 [1]. 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 [2]. 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 [3]. 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 [4]. 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 [4–6].

In addition to the histological similarities, AT/RT has many common radiological and clinical characteristics with medulloblastoma. It commonly affects infants and young children. It can be located both infratentorial and supratentorial although posterior fossa is more common.

Looking at the clinical and pathological similarities between these two entities, it is important to realize that the clinical outcomes of these tumors are somehow different. Over the past 30 years, the overall survival of medulloblastoma has increased from 25 to 65 % [7], while the numbers are still the same for AT/RT with a median survival of almost a year especially when metastases were found at the time of diagnosis, an entity seen in 20 % of the patients [6]. The patients with AT/RT tend to be refractory to standardized therapies, especially chemotherapy for medulloblastoma. A significant portion dies of local recurrence.

Majority of the patients with AT/RT present at an age of less than 3 years, radiation therapy has usually been withheld as a standard treatment option right away from surgery. However, the most recent evidence suggests that long-term survival can be obtained with the use of more intensive and aggressive chemotherapy with adjuvant radiation therapy still presents a particular dilemma as young patients with this disease may experience serious late effects of therapy if with longer follow-up.

The first and the most important step of treating this tumor is achieving the correct diagnosis for directing the patient to the most proper therapy. As approximately two-thirds of the patients with AT/RT have pathologic samples that contain cells resembling medulloblastoma [7]. IHC is the most objective and reliable way to make a differentiation.

The earliest publication for the association of AT/RT with chromosomal abnormalities especially chromosome 22 was from Rorke et al. in 1995 [8]. Through subsequent years, specific gene mutations were identified on a specific locus of the chromosome. The identification of hSNF5/INI1 gene mutation is now used for the definition of the disease.