Imaging characteristics of atypical teratoid-rhabdoid tumor in children compared with medulloblastoma

Primarily solid intraventricular brain tumors

Solid intraventricular-neoplasms are readily seen on cross-sectional images, but the myriad of entities to be considered may make a focused differential diagnosis elusive. Clinical symptoms of patients with intraventricular-tumors are non-specific and are generally related to increased intracranial pressure or hydrocephalus. The objective of this article is to present the most relevant demographic, clinical and imaging features of solid intraventricular-tumors for the purpose of a more comprehensive differential-diagnosis.

Magnetic resonance imaging spectrum of medulloblastoma

INTRODUCTION

Two medulloblastoma variants were recently added to the WHO classification of CNS tumours. We retrospectively analysed the imaging findings of 37 classic and 27 cases of variant medulloblastomas to identify imaging characteristics that might suggest a particular MB subtype.

METHODS

Sixty-four patients from three institutions were included. Location, tumour margins, signal intensities on conventional MRI, enhancement pattern, the presence of haemorrhage, calcifications and hydrocephalus were recorded and analysed. Signal characteristics on diffusion-weighted MR images and MR spectra were evaluated when available.

RESULTS

Thirty-seven classic type of MB (CMB), twelve cases of desmoplastic/nodular medulloblastoma (DMB), nine medulloblastomas with extensive nodularity (MB-EN), five cases of anaplastic and one of large-cell medulloblastoma were included. Fifty of 64 tumours were located in the 4th ventricle region. On T2WI, CMB were all hyperintense, whereas DMB and MB-EN showed isointensity in up to 66%. One third of the classic MB showed only subtle marginal or linear enhancement. All medulloblastoma variants showed marked enhancement.

CONCLUSION

The results of our study suggest: (a) an age-dependent distribution of MB variants, with DMB and MB-EN more common in younger children; (b) a female predominance in DMB; (c) a more common off-midline location in DMB (50%) and MB-EN (33%) variants.

Atypical teratoid/rhabdoid tumors in adult patients: CT and MR imaging features

Primary AT/RT is a rare highly malignant tumor of the CNS, usually occurring in children younger than 5 years of age. The objective of this study was to characterize the CT and MR imaging findings in a series of 5 adult patients with pathologically proved AT/RT. All 5 AT/RTs were supratentorial. In 2 patients who underwent nonenhanced CT, the tumors appeared isoattenuated, and 1 of the 2 tumors contained calcifications. Solid portions of the tumors on MR imaging were isointense on T1-weighted, T2-weighted, and FLAIR images, and 1 case showed restricted diffusion on DWI. The tumors also demonstrated a bandlike rim of strong enhancement surrounding a central cystic area on contrast-enhanced T1-weighted imaging. One tumor was associated with destruction of the calvaria. Although AT/RTs can have nonspecific findings, the tumors in our series were large and isointense on T1-weighted, T2-weighted, and FLAIR images with central necrosis and prominent rim enhancement.

Medulloblastoma: atypical CT and MRI findings in children

Posterior fossa mass lesions in children usually present a diagnostic challenge despite their high frequency and the limited number of differential diagnostic possibilities. Consideration of medulloblastoma within the differential diagnosis of such lesions mandates an aggressive surgical approach as residual tumor is a known risk factor for poor prognosis. Preoperative imaging of the entire neuroaxis is critical given the high propensity of drop metastases. In this pictorial presentation, we review and demonstrate less common features of medulloblastomas to facilitate diagnosis in challenging cases.

Value and limitations of diffusion-weighted imaging in grading and diagnosis of pediatric posterior fossa tumors

DWI reportedly accurately differentiates pediatric posterior fossa tumors, but anecdotal experience suggests limitations. In 3 years, medulloblastoma and JPA were differentiated by DWI alone in 23/26 cases (88%). Ependymoma (n = 5) could not be reliably differentiated from medulloblastoma or JPA. A trend toward increased diffusion restriction in higher grade tumors (1/14 grade I, 7%; 9/12 grade IV, 75%) had too much overlap to predict the grade of individual cases. The overlap in ADC between tumor types appeared partly due to technical factors (in small, heterogeneous, calcific, or hemorrhagic tumors) but also likely reflected true histologic variability, given that our 3 overlap cases included a desmoplastic medulloblastoma, an anaplastic ependymoma, and a JPA with restricted diffusion in its nodule. Simple structural features (macrocystic tumor, location off midline) aided in distinguishing JPA from the other tumors in these cases.

Diffusion-weighted imaging of an atypical teratoid/rhabdoid tumor of the cervical spine

Spinal atypical teratoid/rhabdoid tumor (AT/RT) is a rare, aggressive malignant neoplasm of the central nervous system usually seen in young children and infants. We present diffusion-weighted imaging (DWI) findings for an intradural extramedullary AT/RT in the cervical spine of a 6-year-old boy. High signal on DWI and low apparent diffusion coefficients may represent high cellularity of the tumor. These findings indicated a highly malignant tumor.

Atypical teratoid/rhabdoid tumors of the central nervous system: imaging and clinical findings in 16 children

AIM

To investigate the imaging and clinical findings of central nervous system (CNS) atypical teratoid/rhabdoid tumours (AT/RTs) in children.

MATERIALS AND METHODS

The computed tomography (CT) and magnetic resonance imaging (MRI) findings and clinical records of 16 children with CNS AT/RTs were retrospectively reviewed. Tumour location, size, composition, enhancement pattern, peritumoural oedema, signal intensity (SI) on MRI and CT attenuation were evaluated.

RESULTS

A total of 17 lesions from 16 patients (median age 2.3 years, age range 0.7-15 years) were included in the evaluation. Tumour location was infratentorial for 11 lesions and supratentorial for six lesions. The mean diameter of the largest dimension for a tumour was 4 cm. The tumour was mainly solid in 65% of cases, and solid and cystic or cystic and solid in 35% of cases. The solid component of the tumours had a homogeneous iso SI (n=15) on T2-weighted MRI images and iso SI (n=14) on T1-weighted images. Moderate to strong enhancement of the solid component was noted in most cases. In spite of a large tumour size, peritumoural oedema was minimal or mild except in four cases. Rapid growth of the tumour was demonstrated in three cases. Seven patients died from tumour progression, with a mean survival time of 8.4 months (range 2-12 months).

CONCLUSION

Although the AT/RTs had non-specific imaging findings, the tumours tended to be large in size, have iso SI on T1 and T2-weighted MR images with prominent enhancement, and relatively mild peritumoural oedema. Rapid growth of the tumour was seen during the follow-up period.

Atypical teratoid/rhabdoid tumor of the optic nerve

We report a rare case of atypical teratoid/rhabdoid tumor that presented with imaging findings similar to those of optic pathway glioma. The diagnosis of atypical teratoid/rhabdoid tumor was determined following surgical resection of the tumor by collective histologic and immunohistochemical staining, and cytogenetic analysis. We describe the clinical presentation, neuroimaging findings and pathology, and compare them to those of optic gliomas.