Atypical teratoid rhabdoid tumor (AT/RT) in adults: review of four cases

Abstract

Atypical teratoid/rhabdoid (AT/RT) tumor is a rare, highly malignant tumor of the central nervous system (CNS) most commonly found in children less than 5 years of age. Although the vast majority of cases are diagnosed in young children, there have been isolated case reports in adults. Since its histological appearance can be confused with other tumors, especially in adults, separating AT/RT from other neoplasms may be difficult. In many instances, a reliable diagnosis is not possible without demonstrating the lack of nuclear INI1 protein expression by immunohistochemical methods. The patients (three males and one female) ranged in age from 23 to 42 years (mean age, 32 years). Radiographically, two tumors were localized in the right fronto-parietal region, one was frontal and the other was found in the left temporal lobe. Varying degrees of hydrocephalus and heterogeneous enhancement were present on MRI. In all cases, diagnosis during intraoperative consultation and preliminary diagnosis was different from the final diagnosis after immunohistochemical analysis. Immunohistochemical staining showed that the tumor cells were positive for vimentin and reacted variably for keratin, epithelial membrane antigen (EMA), synaptophysin, neurofilament protein, CD34, and smooth muscle actin (SMA). All were negative for GFAP, S-100, desmin and CD99. Three of the four cases lacked nuclear expression of INI1. One patient is alive with no evidence of disease 17 years after the diagnosis. In adult examples of AT/RT, the diagnosis requires a high index of suspicion, with early tissue diagnosis and a low threshold for investigation with INI1 immunohistochemistry to differentiate this entity from other morphologically similar tumors. Although the prognosis is dismal in pediatric population, long term survival is possible in adult AT/RT cases after surgery and adjuvant radiotherapy and chemotherapy.

Atypical Teratoid/Rhabdoid Tumors in Adult Patients: CT and MR Imaging Features

“…AT/RT was first recognized as a malignant intracranial rhabdoid tumor in an adult patient in 1992 by Horn et al 30 From then on, approximately 30 cases of adult AT/RT have been reported. [18][19][20][21][22][23][24][25][26][27][28][29][30] In contrast to the pediatric neoplasm, most adult CNS rhabdoid tumors are supratentorial, with only 3 tumors located in the cerebellum and 2 in the spinal cord. Most cases were diagnosed on the basis of characteristic histologic and immunohistochemical features.…”

“…This is a component of the SWItch/Sucrose Non-Fermentable chromatin remodeling complex and functions as a tumor suppressor by positively regulating transcription of a particular set of eukaryotic genes, possibly including the c-Myc target genes involved with differentiation and apoptosis. 19,22,24 The loss of expression of INI1 is considered to be diagnostic for AT/RT. 33 The diagnosis of AT/RT was not confirmed by cytogenetic or mRNA analysis, and this omission is a limitation of our retrospective review.…”

“…10,18,19,24 To our knowledge, there are only limited case reports describing the imaging features of this entity in adults. 8,9,18,19,[21][22][23][24][25][26][27][28][29][30][31] The goal of this study was to characterize the CT and MR imaging features of CNS AT/RT in 5 adults. …”

“…17 To our knowledge, only 29 cases of primary AT/RT of the CNS in adults have been reported (On-line Table). [18][19][20][21][22][23][24][25][26][27][28][29][30] The On-line Table summarizes the clinical and imaging data from our patients and from those in the literature.…”

Incidence of atypical teratoid/rhabdoid tumors in children

“…6,7,10,13,15,17,18 Only single cases have been reported in adults. [22][23][24][25][26][27][28][29][30][31][32] Several large, hospital-based series established an atypical teratoid/rhabdoid tumor prevalence of 1% to 2% among pediatric brain tumors, 8,[33][34][35] but population-based data on the incidence of atypical teratoid/rhabdoid tumors in children are not yet available. However, such data provide important insights into the burden of disease and might contribute to patient care.…”