Lynn Gargan

Imaging Characteristics of Atypical Teratoid–Rhabdoid Tumor in Children Compared with Medulloblastoma

OBJECTIVE The purpose of our study was to compare the imaging characteristics of atypical teratoid-rhabdoid tumor with medulloblastoma and seek distinguishing features that can aid in preoperative diagnosis. MATERIALS AND METHODS Preoperative MRI examinations of 55 patients (36 medulloblastomas and 19 atypical teratoid-rhabdoid tumors) were analyzed retrospectively. Imaging characteristics of atypical teratoid-rhabdoid tumor and medulloblastoma were assessed with conventional MRI and CT. Diffusion-weighted imaging (DWI) was available in 27 patients (19 medulloblastomas and eight atypical teratoid-rhabdoid tumors). Apparent diffusion coefficient (ADC) values were calculated for 14 medulloblastomas and six atypical teratoid-rhabdoid tumors. RESULTS Both atypical teratoid-rhabdoid tumors in general and infratentorial atypical teratoid-rhabdoid tumors presented at a younger age than medulloblastomas. Eleven of 19 atypical teratoid-rhabdoid tumors were infratentorial. Cerebellopontine angle (CPA) involvement was more frequent (8/11, 72.7%) in atypical teratoid-rhabdoid tumor than in medulloblastoma (4/36, 11.1%) (p < 0.001). Intratumoral hemorrhage was more common in atypical teratoid-rhabdoid tumor (9/19, 47.4%) than in medulloblastoma (2/36, 5.6%) (p < 0.0001). All atypical teratoid-rhabdoid tumors and all medulloblastomas for which DWI was available displayed increased signal intensity on DWI compared with normal brain parenchyma. The mean ADC values for tumor types were not significantly different. CONCLUSION Atypical teratoid-rhabdoid tumor presents at a younger age than medulloblastoma. Although atypical teratoid-rhabdoid tumor and medulloblastoma display similar imaging characteristics on conventional MRI, CPA involvement and intratumoral hemorrhage are more common in atypical teratoid-rhabdoid tumor. If a pediatric posterior fossa mass that displays restricted diffusion is involving the CPA, atypical teratoid-rhabdoid tumor is a more likely consideration than medulloblastoma.

Study of the MIB-1 Labeling Index as a Predictor of Tumor Progression in Pilocytic Astrocytomas in Children and Adolescents

PURPOSE The pilocytic astrocytoma (PA) is the most common childhood brain tumor. This report examines the MIB-1 labeling index (LI) as a predictor of progression-free survival (PFS) among childhood PAs. PATIENTS AND METHODS Consecutive PAs were examined to determine whether the MIB-1 LI was associated with tumor progression. Other variables evaluated included tumor location, use of adjuvant therapy, extent of resection, and age at diagnosis. RESULTS One hundred forty-one children were identified (mean +/- SD age, 7.6 +/- 4.7 years; range, 0.43 to 18.56 years); 118 children had adequate tissue for MIB-1 immunohistochemistry. The 5-year PFS was 61.25%. By log-rank analysis, an MIB-1 LI of more than 2.0 was associated with shortened PFS (P =.035). Patients with PAs who underwent complete surgical resection, had tumors located in the cerebellum, and were treated with surgery only also had more prolonged PFS (P =.001 for all). Tumors in the optic pathways were associated with a shorter PFS (P =.001). Restricting the evaluation of MIB-1 LI to only incompletely resected tumors revealed an insignificant trend of MIB-1 LI of more than 2.0 having a shortened PFS. Multivariate analysis demonstrated completely resected tumors and tumors located in the cerebellum as less likely to progress (P =.001 and.019, respectively). CONCLUSION Children with PAs with an MIB-1 LI of more than 2.0 have a shortened PFS. PAs that are completely resected and are located in the cerebellum have a prolonged PFS. This initial study suggests that the MIB-1 LI identifies a more aggressive subset of PAs. Further work should focus on elucidating features of pilocytic astocytomas that will identify prospectively children at risk for progression.

Utility of Apparent Diffusion Coefficient Ratios in Distinguishing Common Pediatric Cerebellar Tumors

RATIONALE AND OBJECTIVES The aim of this study was to identify clinically useful tumor/normal brain apparent diffusion coefficient (ADC) ratios for distinguishing common pediatric cerebellar tumors. MATERIALS AND METHODS Review of medical records revealed 79 patients with cerebellar tumors who underwent preoperative magnetic resonance imaging, including diffusion-weighted imaging sequences, and surgery. There were 31 pilocytic astrocytomas, 27 medulloblastomas, 14 ependymomas, and seven atypical teratoid/rhabdoid tumors. ADC values were measured by placing regions of interest on the solid tumor and normal brain parenchyma by two reviewers. Tumor/normal brain ADC ratios were calculated. RESULTS Mean ADC values of the pilocytic astrocytomas were greater than those of ependymomas, whose mean ADC values were greater than those of medulloblastomas and atypical teratoid/rhabdoid tumors. Using a tumor/normal brain ADC ratio threshold of 1.70 to distinguish pilocytic astrocytomas from ependymomas, sensitivity of 92% and specificity of 79% were achieved. A tumor/normal brain ADC ratio threshold of 1.20 enabled the sorting of ependymomas from medulloblastomas with sensitivity of 93% and specificity of 88%. CONCLUSIONS Tumor/normal brain ADC ratios allow the distinguishing of common pediatric cerebellar tumors.

Common Pediatric Cerebellar Tumors: Correlation between Cell Densities and Apparent Diffusion Coefficient Metrics

PURPOSE To test whether there is correlation between cell densities and apparent diffusion coefficient (ADC) metrics of common pediatric cerebellar tumors. MATERIALS AND METHODS This study was reviewed for issues of patient safety and confidentiality and was approved by the Institutional Review Board of the University of Texas Southwestern Medical Center and was compliant with HIPAA. The need for informed consent was waived. Ninety-five patients who had preoperative magnetic resonance imaging and surgical pathologic findings available between January 2003 and June 2011 were included. There were 37 pilocytic astrocytomas, 34 medulloblastomas (23 classic, eight desmoplastic-nodular, two large cell, one anaplastic), 17 ependymomas (13 World Health Organization [WHO] grade II, four WHO grade III), and seven atypical teratoid rhabdoid tumors. ADCs of solid tumor components and normal cerebellum were measured. Tumor-to-normal brain ADC ratios (hereafter, ADC ratio) were calculated. The medulloblastomas and ependymomas were subcategorized according to the latest WHO classification, and tumor cellularity was calculated. Correlation was sought between cell densities and mean tumor ADCs, minimum tumor ADCs, and ADC ratio. RESULTS When all tumors were considered together, negative correlation was found between cellularity and mean tumor ADCs (ρ = -0.737, P < .05) and minimum tumor ADCs (ρ = -0.736, P < .05) of common pediatric cerebellar tumors. There was no correlation between cellularity and ADC ratio. Negative correlation was found between cellularity and minimum tumor ADC in atypical teratoid rhabdoid tumors (ρ = -0.786, P < .05). In atypical teratoid rhabdoid tumors, no correlation was found between cellularity and mean tumor ADC and ADC ratio. There was no correlation between the ADC metrics and cellularity of the pilocytic astrocytomas, medulloblastomas, and ependymomas. CONCLUSION Negative correlation was found between cellularity and ADC metrics of common pediatric cerebellar tumors. Although ADC metrics are useful in the preoperative diagnosis of common pediatric cerebellar tumors and this utility is generally attributed to differences in cellularity of tumors, tumor cellularity may not be the sole determinant of the differences in diffusivity.

Predictors of tumor progression among children with gangliogliomas. Clinical article.

OBJECT Few reports describe the outcome and prognostic factors for children with gangliogliomas. The objective of this report was to describe the progression-free survival (PFS) for children with low-grade gangliogliomas and identify risk factors for tumor progression. METHODS A retrospective study was performed in children with low-grade gangliogliomas who were evaluated and treated in the neuro-oncology department between 1986 and 2006 to determine risk factors for subsequent tumor progression. RESULTS A total of 38 children with newly diagnosed gangliogliomas were included in this report. Thirty-four children were treated with surgery alone, 3 with subtotal resection and radiation therapy, and 1 with subtotal resection and chemotherapy. The follow-up ranged from 4 months to 15.8 years (mean 5.7+/-4.2 years [+/-SD]). Seven children have experienced tumor progression, and 1 child died after his tumor subsequently underwent malignant transformation. The 5-year PFS was calculated to be 81.2% using Kaplan-Meier survival analysis. Initial presentation with seizures (p=0.004), tumor location in the cerebral hemisphere (p=0.020), and complete tumor resection (p=0.035) were associated with prolonged PFS. Further analysis of the above significant variables by a Cox regression model identified initial presentation with seizures as being associated with prolonged PFS (p=0.028). CONCLUSIONS The PFS and overall survival of children with gangliogliomas are good. Tumors located in the cerebral hemispheres, the achievement of total resection, and seizures at presentation were associated with prolonged PFS. Cox regression analysis identified presenting symptoms including seizures as significant predictive factors of PFS. Prospective studies with larger numbers of children are needed to define the significant factors of tumor progression.

Survey of long‐term follow‐up programs in the United States for survivors of childhood brain tumors

Despite recognition that childhood brain tumor survivors often suffer multiple late effects following therapy, little is known regarding the long‐term follow‐up (LTFU) programs for these patients.

Pleomorphic Xanthoastrocytoma of Childhood: MR Imaging and Diffusion MR Imaging Features

BACKGROUND AND PURPOSE: Pleomorphic xanthoastrocytomas are rare astrocytic neoplasms of childhood and young adulthood. The purpose of this retrospective review was to evaluate MR imaging features of pediatric pleomorphic xanthoastrocytomas with an emphasis on diffusion MR imaging. MATERIALS AND METHODS: Review of the neuro-oncology data base revealed 11 pediatric patients (range, 4.7–16.1 years) with pleomorphic xanthoastroacytomas with 9 of these patients having preoperative MR imaging available. Six patients had preoperative diffusion MR imaging. Demographics, histopathology slides, conventional imaging characteristics (location, cystic component, hemorrhage, enhancement, vasogenic edema, inner table scalloping), and ADC metrics (mean tumor ADC and tumor to normal brain ADC ratio) were evaluated. RESULTS: Three pleomorphic xanthoastrocytomas had anaplastic features. Ten tumors were supratentorial. Two-thirds (6 of 9) of all tumors were either predominantly cystic or had cystic components, and three-fourths (6 of 8) of the supratentorial tumors had associated inner table scalloping. Seven of the 9 tumors had marked vasogenic edema (>10 mm). Mean tumoral ADC (n = 7) was 912 ± 219 × 10−6 mm2/s (min–max: 617–1189). The tumor to normal brain ADC ratio was 1.14 ± 0.26 (min–max: 0.75–1.47). CONCLUSIONS: Pleomorphic xanthoastrocytoma should be entertained in the differential diagnosis of peripheral supratentorial tumors that appear during childhood. Cysts, inner table scalloping, and marked vasogenic edema are relatively frequent features. Relatively low ADC values and ADC ratios are not uncommon in pleomorphic xanthoastrocytoma.

Proliferative and metabolic markers in incompletely excised pediatric pilocytic astrocytomas—an assessment of 3 new variables in predicting clinical outcome

Although pilocytic astrocytoma (PA) is the most common brain tumor diagnosed in children, few prognostic variables have been delineated that stratify the risk of clinical progression in patients with this tumor. In this study, the MIB-1 labeling index was compared with 2 other immunohistochemical markers of cell proliferation, phospho-histone H3 (PHH3) and mini-chromosomal maintenance protein 2 (MCM2) in 80 incompletely resected PAs to see which was best able to identify patients at risk for tumor progression. 0(6)-Methylguanine-DNA methyltransferase (MGMT) protein expression, which has been predictive of progression-free survival (PFS) in high-grade gliomas in children, was also evaluated in these cases. The mean follow-up period was 7.81 ± 3.9 years, and 42.8% of tumors have shown progression at the time of censoring. A MIB-1 labeling index ≥2.0 was associated with shortened PFS as a grouped variable by log-ranked analysis (P = .03) and by Cox regression analysis as a continuous variable (P = .007). None of the other potential biomarkers was significantly predictive of PFS. Although the amount of MCM2 staining correlated with the MIB-1 labeling index (P < .001), MCM2 reactivity was not independently associated with outcome. We conclude that MIB-1 labeling remains the best predictor of PFS in pediatric PAs.

Transrectal ultrasound and fluoroscopy-guided drainage of deep pelvic collections in children

PURPOSE Pediatric deep pelvic abscesses generally occur as a complication of perforated appendicitis or after laparoscopic appendectomy. We describe our technique and experience in imaging-guided transrectal drainage (TRD) of deep pelvic abscesses in children. METHODS From January 2005 to November 2008, imaging-guided TRD was attempted in 29 children. The procedure records and medical records were reviewed retrospectively. RESULTS Twenty-nine TRD procedures were performed in 17 males and 12 female patients. The mean age was 11.8 years (range, 3.8-15.9 years). Fourteen patients required TRD after an abdominal operative procedure: laparoscopic appendectomy (n = 9), open appendectomy (n = 3), exploratory celiotomy for gunshot wound (n = 1), and exploratory celiotomy with intestinal resection for adhesive bowel obstruction (n = 1). Fifteen patients were referred for TRD as initial therapy for deep pelvic fluid collections: perforated appendicitis (n = 14) and Crohn perforation (n = 1). Twenty-seven (93.1%) procedures were successful, described as either placement of a TRD catheter or aspiration of the deep pelvic fluid using transrectal approach. There were no procedure-related complications. CONCLUSIONS Imaging-guided TRD in children is a safe and easy procedure that allows drainage of deep pelvic abscesses that are otherwise not easily accessible.

Diffusion MRI Improves the Accuracy of Preoperative Diagnosis of Common Pediatric Cerebellar Tumors among Reviewers with Different Experience Levels

DWI studies of 96 cerebellar pediatric tumors were analyzed by neuroradiologists and residents in radiology during 2 sessions, one that included the DWI studies and one that did not. These observers were asked to categorize the masses as: astrocytoma, medulloblastoma, ependymoma, or atypical teratoid/rhabdoid tumor. The addition of DWI resulted in significant improvement in the diagnosis of all tumors except ependymoma among all reviewers with different levels of experience. BACKGROUND AND PURPOSE: Although utility of diffusion MR imaging in the preoperative diagnosis of common pediatric cerebellar tumors is generally recognized, its added value has not been systematically studied previously. The purpose of this study was to evaluate the impact of diffusion MR imaging on the accuracy of preoperative diagnosis of common pediatric cerebellar tumors among reviewers with different experience levels. MATERIALS AND METHODS: Review of the neuro-oncology data base yielded 96 patients whose preoperative brain MR imaging included both diffusion MR imaging (b = 1000 s/mm2) and ADC maps. There were 38 pilocytic astrocytomas, 33 medulloblastomas, 17 ependymomas, and 8 atypical teratoid/rhabdoid tumors. Six reviewers (4 residents, 2 neuroradiologists) evaluated the examinations. Two sessions were conducted with each reviewer, without and with diffusion MR imaging data on 2 separate days. The impact of diffusion MR imaging on accuracy of diagnoses was assessed. RESULTS: In choosing the correct diagnosis of the 4 alternatives, performances of 5 of the 6 reviewers improved significantly with inclusion of the diffusion MR imaging data, from 63%–77% (P = .0003–.0233). The performance of 1 reviewer also improved, but the difference did not attain statistical significance (P = .1944). Inclusion of diffusion MR imaging data improved the likelihood of rendering a correct diagnosis (odds ratio = 3.16, 95% confidence interval = 2.07–4.00) over all tumor types. When embryonal tumors were regarded as a single group, the rate of correct diagnosis increased from 66%–83% with diffusion MR imaging data, and performances of all of the reviewers improved significantly (P = .0001–.05). The improvement in performances resulted from increased correct diagnoses of pilocytic astrocytomas, medulloblastomas, and atypical teratoid/rhabdoid tumors. There was no improvement in the correct diagnoses of ependymomas with inclusion of the diffusion MR imaging data. CONCLUSIONS: Diffusion MR imaging improves accuracy of preoperative diagnosis of common pediatric cerebellar tumors significantly among reviewers with differing experience levels.