Primary intracranial atypical teratoid/rhabdoid tumors of infancy and childhood: MRI features and patient outcomes

Abstract

Background and purpose: Primary atypical teratoid/rhabdoid tumors (AT/RTs) are rare malignant intracranial neoplasms, usually occurring in young children. The objectives of this study were to characterize the MR imaging features and locations of primary intracranial AT/RTs, to determine the frequency of disseminated disease in the central nervous system (CNS) at diagnosis and postoperatively, and to assess patient outcomes.

Methods: The preoperative cranial MR images of 13 patients with AT/RTs were retrospectively reviewed for evaluation of lesion location, size, MR signal intensity and enhancement characteristics, and the presence of disseminated intracranial tumor. Postoperative MR images of the head and spine for 17 patients were reviewed for the presence of locally recurrent or residual tumor and disseminated neoplasm. Imaging data were correlated with patient outcomes.

Results: Patients ranged in age from 4 months to 15 years (median age, 2.9 years). Primary AT/RTs were intra-axial in 94% of patients. The single primary extra-axial lesion was located in the cerebellopontine angle cistern. AT/RTs were infratentorial in 47%, supratentorial in 41%, and both infra- and supratentorial in 12%. A germ-line mutation of the hSNF5/INI1 tumor-suppressor gene was responsible for the simultaneous occurrence of an intracranial AT/RT and a malignant renal rhabdoid tumor in a 4-month-old patient. Mean tumor sizes were 3.6 x 3.8 x 3.9 cm. On short TR images, AT/RTs typically had heterogeneous intermediate signal intensity, as well as zones of low (54%), high (8%), or both low and high (31%) signal intensity from cystic and/or necrotic regions, hemorrhage, or both, respectively. On long TR/long TE images, solid portions of AT/RTs typically had heterogeneous intermediate-to-slightly-high signal intensity with additional zones of high (54%) or both high and low signal intensity (38%), secondary to cystic and/or necrotic regions, edema, prior hemorrhage, and/or calcifications. AT/RT had isointense and/or slightly hyperintense signal intensity relative to gray matter on fluid-attenuated inversion-recovery (FLAIR) and long TR/long TE images, and showed restricted diffusion. All except 1 AT/RT showed contrast enhancement. The fraction of tumor volume showing enhancement was greater than two thirds in 58%, between one third and two thirds in 33%, and less than one third in 9%. Disseminated tumor in the leptomeninges was seen with MR imaging in 24% of patients at diagnosis/initial staging and occurred in another 35% from 4 months to 2.8 years (mean, 1.1 years) after surgery and earlier imaging examinations with negative findings. The overall 1-year and 5-year survival probabilities were 71% and 28%, respectively. Patients with MR imaging evidence of disseminated leptomeningeal tumor had a median survival rate of 16 months compared with 149 months for those without disseminated tumor (P < .004, logrank test).

Conclusion: AT/RTs are typically intra-axial lesions, which can be infra- and/or supratentorial. The unenhanced and enhanced MR imaging features of AT/RT are often variable secondary to cystic/necrotic changes, hemorrhage, and/or calcifications. Poor prognosis is associated with MR imaging evidence of disseminated leptomeningeal tumor.

Fig 1.

MR images of a 2-year-old girl with a germ-line mutation of the hSNF5/INI1 gene and AT/RT in the vermis extending into the fourth ventricle. A, Sagittal (TR/TE, 520/10) MR image shows the tumor to have intermediate and low signal intensity. The tumor invades the dorsal brain stem. B, Axial (TR/TE, 5700/90) MR image shows the tumor to have heterogeneous intermediate-to-slightly-high signal intensity that is slightly hyperintense relative to gray matter, as well as zones of high signal intensity representing cystic/necrotic regions. Abnormal high signal intensity is also seen in the dorsal pons and left middle cerebellar peduncle, consistent with tumor invasion. C, Axial (TR/TE, 680/22) MR image shows the tumor to have solid-enhancing and nonenhancing cystic/necrotic components. Irregular enhancing margins of the lesion are seen at the dorsal pons and left middle cerebellar peduncle, consistent with tumor invasion. This patient died 1.6 years after diagnosis from locally recurrent and disseminated tumor. D, Axial CT image shows the solid portion of the AT/RT to have attenuation slightly higher than that of gray matter. Low-attenuation cystic/necrotic zones and several tiny calcifications are also present.

Fig 2.

MR images of a 10-year-old boy with AT/RT in the vermis, extending into the fourth ventricle. A, Axial (TR/TE, 600/11) MR image shows the tumor to have mixed intermediate signal intensity as well as irregular zones of high signal intensity secondary to hemorrhage (methemoglobin). B, Axial (TR/TE, 3500/108) MR image shows the tumor to have heterogeneous mixed low, intermediate, and high signal intensity. C, Axial (TR/TE, 500/29) MR image shows contrast enhancement in less than two thirds of the AT/RT. This patient is alive without evidence of disease 9 years after surgery/initial diagnosis.

Fig 3.

MR images of a 1.3-year-old boy with AT/RT in the right cerebral peduncle. A, Axial (TR/TE, 600/10) MR image shows the tumor to have intermediate signal intensity. B, Axial (TR/TE, 4000/105) MR image shows the tumor to have heterogeneous intermediate-to-slightly-high signal intensity, which includes zones that are isointense or slightly hyperintense to gray matter. C, Axial (TR/TE, 700/22) fat-suppressed MR image shows prominent homogeneous contrast enhancement of the primary lesion as well as abnormal subarachnoid enhancement in the interpeduncular cistern and along the sulci adjacent to frontal lobes (arrows), representing disseminated leptomeningeal tumor. This patient died 4 months after diagnosis.

Fig 4.

MR images of 3.4-year-old boy with a hemorrhagic AT/RT in the frontal lobe. A, Sagittal (TR/TE, 520/10) MR image shows a hemorrhagic lesion in the inferior left frontal lobe. B, Sagittal (TR/TE, 600/22) MR image shows edge enhancement of the lesion. C and D, Sagittal (C) (TR/TE, 520/10) and axial (D) (TR/TE, 520/10) MR images obtained 7 months after A, -B show marked interval enlargement of the lesion, which has heterogeneous mixed low, intermediate, and high signal intensity involving the inferior portions of both frontal lobes. E, Axial (TR/TE, 5700/90) MR image shows the tumor to have mixed low, intermediate, and high signal intensity, with evidence of edema in the surrounding brain tissue. F, Axial (TR/TE, 600/22) MR image shows prominent heterogeneous contrast enhancement of the tumor with irregular lobulated margins. This patient underwent partial resection of the AT/RT, subsequently had disseminated leptomeningeal tumor, and died 3.3 years after surgery/initial diagnosis. G, Axial CT image shows the lesion to have intermediate attenuation with multiple calcifications and zones of low attenuation.

Fig 5.

MR images of a 4-year-old girl with a constitutional ring 22 chromosome and AT/RT involving the septum pellucidum, with extension into the lateral ventricles. A, Axial (TR/TE, 450/18) MR image shows the tumor to have intermediate signal intensity with several small zones of low signal intensity. B, Axial (TR/TE, 4000/105) MR image shows the tumor to have heterogeneous predominantly intermediate-to-slightly-high signal intensity that is isointense to gray matter, as well as small zones of high and low signal intensity. C, Axial (TR/TE, 450/31) MR image shows irregular heterogeneous contrast enhancement of less than two thirds of the primary AT/RT. This patient had subtotal resection of the tumor and subsequently had locally recurrent disease and disseminated leptomeningeal tumor. She died 14 months after surgery/initial diagnosis.

Fig 6.

MR images of a 4-month-old female infant with a germ-line mutation of the hSNF5/INI1 gene with synchronous AT/RT, showing contiguous involvement of the pineal gland, dorsal midbrain, and upper cerebellum and a malignant rhabdoid tumor involving the left kidney. A, Sagittal (TR/TE, 570/14) MR image shows the tumor to have predominantly intermediate signal intensity with several small zones of high signal intensity. B, Sagittal (TR/TE, 750/22) MR image shows only minimal contrast enhancement in less than one third of the tumor. C, Axial (TR/TE, 3710/105) MR image shows the tumor to have intermediate-to-slightly-high signal intensity that is isointense to gray matter, as well as a small zone of high signal intensity.

Fig 7.

MR images of a 10-month-old female infant with an extra-axial AT/RT in the right cerebellopontine angle cistern, extending into the right internal auditory canal (arrows). A, Axial (TR/TE, 550/14) MR image shows the tumor to have intermediate signal intensity with a zone of low signal intensity medially. B, Axial (TR/TE, 600/22) MR image shows prominent enhancement of the solid portion of the lesion. This patient had subtotal resection followed by chemotherapy and died 1 month after surgery from sepsis related to immunosuppression from chemotherapy.

Fig 8.

MR images of an 8-month-old female infant with AT/RT involving the pineal gland A, Axial (TR/TE, 4000/105) MR image shows the tumor to have heterogeneous intermediate-to-slightly-high signal intensity with regions that are isointense and slightly hyperintense to gray matter, as well as a small zone of high signal intensity. B, Axial FLAIR (TR/TE/TI, 9000/119/2200) MR image shows the tumor to have mostly intermediate signal intensity that is isointense to gray matter. C, Axial (TR/TE, 800/20) fat-suppressed MR image with magnetization transfer shows no contrast enhancement of the primary lesion. This patient had subtotal resection of the primary lesion followed by chemotherapy. The patient had subsequent local recurrence and disseminated leptomeningeal tumor and died 7 months after initial diagnosis.

Fig 9.

MR images of 4-year-old boy with AT/RT involving the vermis A, Axial FLAIR (TR/TE/TI, 9000/119/2200) MR image shows the tumor to have mostly intermediate signal intensity that is isointense to gray matter. B, Axial (TR/TE, 6000/99) MR image shows the tumor to have mostly intermediate-to-slightly-high signal intensity that is slightly hyperintense to gray matter, as well as small zones of high signal intensity. C, Axial (TR/TE, 800/20) fat-suppressed MR image with magnetization transfer shows prominent slightly heterogeneous contrast enhancement of the tumor. This patient had gross total resection of the primary lesion followed by chemotherapy and has been disease-free for 4 years. D, Axial DWI (b = 1000) shows the lesion to have high signal intensity. E, Axial ADC map shows low signal intensity in the lesion, indicating restricted diffusion of water within the AT/RT.