18F-FSPG PET/CT Imaging of System xC- Transporter Activity in Patients with Primary and Metastatic Brain Tumors.

Background The PET tracer (4S)-4-(3-[18F]fluoropropyl)-l-glutamate (18F-FSPG) targets the system xC- cotransporter, which is overexpressed in various tumors. Purpose To assess the role of 18F-FSPG PET/CT in intracranial malignancies. Materials and Methods Twenty-six patients (mean age, 54 years ± 12; 17 men; 48 total lesions) with primary brain tumors (n = 17) or brain metastases (n = 9) were enrolled in this prospective, single-center study (ClinicalTrials.gov identifier: NCT02370563) between November 2014 and March 2016. A 30-minute dynamic brain 18F-FSPG PET/CT scan and a static whole-body (WB) 18F-FSPG PET/CT scan at 60-75 minutes were acquired. Moreover, all participants underwent MRI, and four participants underwent fluorine 18 (18F) fluorodeoxyglucose (FDG) PET imaging. PET parameters and their relative changes were obtained for all lesions. Kinetic modeling was used to estimate the 18F-FSPG tumor rate constants using the dynamic and dynamic plus WB PET data. Imaging parameters were correlated to lesion outcomes, as determined with follow-up MRI and/or pathologic examination. The Mann-Whitney U test or Student t test was used for group mean comparisons. Receiver operating characteristic curve analysis was used for performance comparison of different decision measures. Results 18F-FSPG PET/CT helped identify all 48 brain lesions. The mean tumor-to-background ratio (TBR) on the whole-brain PET images at the WB time point was 26.6 ± 24.9 (range: 2.6-150.3). When 18F-FDG PET was performed, 18F-FSPG permitted visualization of non-18F-FDG-avid lesions or allowed better lesion differentiation from surrounding tissues. In participants with primary brain tumors, the predictive accuracy of the relative changes in influx rate constant Ki and maximum standardized uptake value to discriminate between poor and good lesion outcomes were 89% and 81%, respectively. There were significant differences in the 18F-FSPG uptake curves of lesions with good versus poor outcomes in the primary brain tumor group (P < .05) but not in the brain metastases group. Conclusion PET/CT imaging with (4S)-4-(3-[18F]fluoropropyl)-l-glutamate (18F-FSPG) helped detect primary brain tumors and brain metastases with a high tumor-to-background ratio. Relative changes in 18F-FSPG uptake with multi-time-point PET appear to be helpful in predicting lesion outcomes. Clinical trial registration no. NCT02370563 © RSNA, 2022 Online supplemental material is available for this article.

Salivary Gland NUT Carcinoma with Prolonged Survival in Children: Case Illustration and Systematic Review of Literature.

NUT (midline) carcinoma is a rare, highly aggressive, poorly differentiated carcinoma that characteristically harbors a rearrangement of the NUTM1 gene. Most of these tumors occur in adolescents and young adults, arise from the midline structures of the thorax, head, and neck, and are associated with extremely poor outcomes. Rare cases originating from salivary glands have been reported with clinicopathologic features comparable to NUT carcinoma of other sites. Outcome studies regarding this subgroup are currently lacking. We report a case of NUT carcinoma arising in a submandibular gland of a 12-year-old boy. Diagnosis was confirmed by fluorescence in situ hybridization demonstrating fusion of the BRD4 (19p13.12) and NUTM1 (15q14) gene loci. A systematic review of all previously reported salivary gland NUT carcinomas (n = 15) showed exclusive occurrence of pediatric cases (n = 6) in males compared to adult patients (n = 9, male: female = 1:2; p < 0.05). The median survival was 24 and 4 months for pediatric and adult patients, respectively (95% confidence interval was 8-24 and 1-7 months, respectively; p < 0.01). The 1-year overall survival was 67% for pediatric and 11% for adult patients. Among all NUT carcinomas, pediatric salivary gland tumors may represent a distinct clinical subset associated with male predilection and comparatively prolonged survival.

A Case of Cushing's Syndrome due to Ectopic Adrenocorticotropic Hormone Secretion from Esthesioneuroblastoma with Long Term Follow-Up after Resection.

We present a case of a 52-year-old male who developed Cushing's Syndrome due to ectopic adrenocorticotrophic hormone (ACTH) secretion from a large esthesioneuroblastoma (ENB) of the nasal sinuses. The patient initially presented with polyuria, polydipsia, weakness, and confusion. Computed tomography scan of the head and magnetic resonance imaging showed a 7 cm skull base mass centered in the right cribriform plate without sella involvement. Work-up revealed ACTH-dependent hypercortisolemia, which did not suppress appropriately after high-dose dexamethasone. Subsequent imaging of the chest, abdomen, and pelvis did not reveal other possible ectopic sources of ACTH secretion besides the ENB. His hospital course was complicated by severe hypokalemia and hyperglycemia before successful surgical resection of the tumor, the biopsy of which showed ENB. Postoperatively, his ACTH level dropped below the limit of detection. In the ensuing 4 months, he underwent adjuvant chemoradiation with carboplatin and docetaxel with good response and resolution of hypokalemia and hyperglycemia, with no sign of recurrence as of 30 months postoperatively. His endogenous cortisol production is rising but has not completely recovered.

Neurosarcoidosis Presenting as Aseptic Meningitis in an Immunosuppressed Renal Transplant Recipient.

BACKGROUND: Sarcoidosis is a presumptive autoimmune disorder characterized by the presence of noncaseating granulomas and is usually treated successfully with immunosuppression. METHODS AND RESULTS: Here, we describe the case of a 63-year-old male renal transplant recipient with a remote history of pulmonary sarcoidosis on chronic immunosuppression who developed recurrent aseptic meningitis and underwent brain biopsy revealing a diagnosis of neurosarcoidosis. CONCLUSIONS: This case highlights the possibility of recurrence of sarcoidosis in the setting of maintenance immunosuppression, the need for heightened awareness of alternative sites of recurrence of autoimmune disease, and future studies to determine the underlying mechanism of recurrence in organ transplant recipients.

Bone morphogenetic protein signaling promotes tumorigenesis in a murine model of high-grade glioma.

BACKGROUND: Improved therapies for high-grade glioma (HGG) are urgently needed as the median survival for grade IV gliomas is only 15 months. Bone morphogenetic protein (BMP) signaling plays critical and complex roles in many types of cancer, including glioma, with most of the recently published work focusing on BMP-mediated regulation of glioma stem cells (GSCs). We hypothesized that BMP signaling may be an important modulator of tumorigenic properties in glioma cells outside of the GSC compartment. METHODS: We used a human HGG tissue microarray and performed immunohistochemistry for phospho-Smads1,5,8. To examine the role of BMP signaling in tumorigenic astrocytes, transgenic mice were used to delete the BMP type IA receptor (Bmpr1a) and generate astrocytes transformed with oncogenic Ras and homozygous deletion of p53. The cells were transplanted orthotopically into immunocompetent adult host mice. RESULTS: First we established that BMP signaling is active within the vast majority of HGG tumor cells. Mice implanted with BMPR1a-knockout transformed astrocytes showed an increase in median survival compared with mice that received BMPR1a-intact transformed astrocytes (52.5 vs 16 days). In vitro analysis showed that deletion of BMPR1a in oncogenic astrocytes resulted in decreased proliferation, decreased invasion, decreased migration, and increased expression of stemness markers. In addition, inhibition of BMP signaling in murine cells and astrocytoma cells with a small molecule BMP receptor kinase inhibitor resulted in similar tumor suppressive effects in vitro. CONCLUSION: BMP inhibition may represent a viable therapeutic approach in adult HGG.

Preclinical TSPO Ligand PET to Visualize Human Glioma Xenotransplants: A Preliminary Study.

Current positron emission tomography (PET) imaging biomarkers for detection of infiltrating gliomas are limited. Translocator protein (TSPO) is a novel and promising biomarker for glioma PET imaging. To validate TSPO as a potential target for molecular imaging of glioma, TSPO expression was assayed in a tumor microarray containing 37 high-grade (III, IV) gliomas. TSPO staining was detected in all tumor specimens. Subsequently, PET imaging was performed with an aryloxyanilide-based TSPO ligand, [18F]PBR06, in primary orthotopic xenograft models of WHO grade III and IV gliomas. Selective uptake of [18F]PBR06 in engrafted tumor was measured. Furthermore, PET imaging with [18F]PBR06 demonstrated infiltrative glioma growth that was undetectable by traditional magnetic resonance imaging (MRI). Preliminary PET with [18F]PBR06 demonstrated a preferential tumor-to-normal background ratio in comparison to 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG). These results suggest that TSPO PET imaging with such high-affinity radiotracers may represent a novel strategy to characterize distinct molecular features of glioma growth, as well as better define the extent of glioma infiltration for therapeutic purposes.

Genomic Analysis of the BMP Family in Glioblastomas.

Glioblastoma multiforme (GBM) is a grade IV glioma with a median survival of 15 months. Recently, bone morphogenetic protein (BMP) signaling has been shown to promote survival in xenograft murine models. To gain a better understanding of the role of BMP signaling in human GBMs, we examined the genomic alterations of 90 genes associated with BMP signaling in GBM patient samples. We completed this analysis using publically available datasets compiled through Te Cancer Genome Atlas and the Glioma Molecular Diagnostic Initiative. Here we show how mRNA expression is altered in GBM samples and how that is associated with patient survival, highlighting both known and novel associations between BMP signaling and GBM biology.

Glycan engagement dictates hydrocephalus induction by serotype 1 reovirus.

UNLABELLED: Receptors expressed on the host cell surface adhere viruses to target cells and serve as determinants of viral tropism. Several viruses bind cell surface glycans to facilitate entry, but the contribution of specific glycan moieties to viral disease is incompletely understood. Reovirus provides a tractable experimental model for studies of viral neuropathogenesis. In newborn mice, serotype 1 (T1) reovirus causes hydrocephalus, whereas serotype 3 (T3) reovirus causes encephalitis. T1 and T3 reoviruses engage distinct glycans, suggesting that glycan-binding capacity contributes to these differences in pathogenesis. Using structure-guided mutagenesis, we engineered a mutant T1 reovirus incapable of binding the T1 reovirus-specific glycan receptor, GM2. The mutant virus induced substantially less hydrocephalus than wild-type virus, an effect phenocopied by wild-type virus infection of GM2-deficient mice. In comparison to wild-type virus, yields of mutant virus were diminished in cultured ependymal cells, the cell type that lines the brain ventricles. These findings suggest that GM2 engagement targets reovirus to ependymal cells in mice and illuminate the function of glycan engagement in reovirus serotype-dependent disease. IMPORTANCE: Receptor utilization strongly influences viral disease, often dictating host range and target cell selection. Different reovirus serotypes bind to different glycans, but a precise function for these molecules in pathogenesis is unknown. We used type 1 (T1) reovirus deficient in binding the GM2 glycan and mice lacking GM2 to pinpoint a role for glycan engagement in hydrocephalus caused by T1 reovirus. This work indicates that engagement of a specific glycan can lead to infection of specific cells in the host and consequent disease at that site. Since reovirus is being developed as a vaccine vector and oncolytic agent, understanding reovirus-glycan interactions may allow manipulation of reovirus glycan-binding properties for therapeutic applications.

Retinal metastasis from unknown primary: diagnosis, management, and clinicopathologic correlation.

A 75-year-old man was incidentally found to have a yellow-white retinal lesion with scattered hemorrhages. He was empirically treated elsewhere for viral retinitis without resolution and later transferred to the Vanderbilt Eye Institute, where retinal biopsy with silicone oil tamponade showed retinal metastasis. He had no prior history of cancer, and multiple systemic imaging evaluations failed to identify a primary site. Histopathology and immunohistochemistry of the biopsy were consistent with non-small-cell lung carcinoma. Due to the radiation-attenuating properties of silicone oil, the patient underwent silicone oil removal prior to receiving external beam radiotherapy (EBRT). The retinal metastasis responded completely to EBRT, and at final follow-up, 18 months after initial presentation, no primary tumor has been identified.

Critical functions of RhoB in support of glioblastoma tumorigenesis.

BACKGROUND: RhoB is a member of the Rho small GTPase family that regulates cytoskeletal dynamics and vesicle trafficking. The RhoB homologs, RhoA and RhoC, have been shown to promote cancer progression and metastasis. In contrast, the functions of RhoB in human cancers are context dependent. Although expression of RhoB inversely correlates with disease progression in several epithelial cancers, recent data suggest that RhoB may support malignant phenotypes in certain cancer types. METHODS: We assessed RhoB protein levels in glioma surgical specimens and patient-derived xenografts. The roles of RhoB in glioblastoma were determined by loss-of-function and gain-of-function assays in vitro and in vivo. The impact on p53 and STAT3 signaling was investigated. RESULTS: RhoB expression was similar in tumor specimens compared with normal neural tissues obtained from epilepsy surgery. RhoB was expressed in the vast majority of xenograft tumors and spheroid cultures. Knockdown of RhoB induced cell-cycle arrest and apoptosis and compromised in vivo tumorigenic potential. However, overexpression of wild-type RhoB or a constitutively active mutant (RhoB-V14) did not significantly affect cell growth, which suggests that RhoB is not a rate-limiting oncogenic factor and is consistent with the scarcity of RhoB mutations in human cancer. Knockdown of RhoB reduced basal STAT3 activity and impaired cytokine-induced STAT3 activation. In glioblastoma tumors retaining wild-type p53, depletion of RhoB also activated p53 and induced expression of p21(CIP1) (/WAF1). CONCLUSIONS: Our data suggest that RhoB belongs to an emerging class of "nononcogene addiction" factors that are essential for maintenance of malignant phenotypes in human cancers.

Cell of origin determines tumor phenotype in an oncogenic Ras/p53 knockout transgenic model of high-grade glioma.

Human high-grade gliomas (HGGs) are known for their histologic diversity. To address the role of cell of origin in glioma phenotype, transgenic mice were generated in which oncogenic Ras and p53 deletion were targeted to neural stem/progenitor cells (NSPCs) and mature astrocytes. The hGFAP-Cre/Kras/p53 mice develop multifocal HGGs that vary histopathologically and with respect to the expression of markers associated with NSPCs. One HGG pattern strongly expressed markers of NSPCs and arose near the subventricular zone. Additional nonoverlapping patterns that recapitulate human HGG variants were present simultaneously in the same brain. These neoplastic foci were more often cortical or leptomeningeal based, and the neoplastic cells lacked expression of NSPC markers. To determine whether cell of origin determines tumor phenotype, astrocytes and NSPCs were harvested from neonatal mutant pups. Onorthotopic transplantation, early-passage astrocytes and NSPCs formed tumors that differed in engraftment rates, latency to clinical signs, histopathology, and protein expression. Astrocyte-derivedtumors were more aggressive, had giant-cell histology, and glial fibrillary acidic protein expression. The NSPC-derived tumors retained NSPC markers and showed evidence of differentiation along astrocytic, oligodendroglial, and neuronal lineages. These results indicate that identical tumorigenic stimuli produce markedly different glioma phenotypes, depending on the differentiation status of the transformed cell.

Identification of blood protein biomarkers that aid in the clinical assessment of patients with malignant glioma.

Analyzing molecular biomarkers using blood is an important approach for clinical assessment of malignant glioma. We investigated a molecular proteomic biomarker-based approach for glioblastoma using patients' blood samples. The expression levels of a list of candidate proteins were quantified in plasma and serum samples from two different cohorts of patients with malignant glioma and normal controls. The biological function was studied for one of the identified markers. Additionally, the prognostic significance of protein marker expression was measured by survival analysis. As a result, protein biomarkers associated with malignant glioma were identified from the blood specimens and five of the protein biomarkers were common to both cohorts. Immunohistochemical analysis demonstrated that many of the protein biomarkers identified in peripheral blood specimens were expressed in malignant gliomas. Staining levels for one of the biomarkers, MIP-1α, was found to correlate with WHO grade among invasive gliomas, and we demonstrate that MIP-1α promotes human glioblastoma cell proliferation and migration. Additionally, four prognostic protein biomarkers were identified. In conclusion, we demonstrate that both peripheral blood plasma and serum specimens are highly valuable and complementary to each other in the quest for protein biomarkers of malignant glioma. Sets of novel protein biomarkers were identified that may aid in the diagnosis and prognosis of patients with malignant glioma.

Loss of one Tgfbr2 allele in fibroblasts promotes metastasis in MMTV: polyoma middle T transgenic and transplant mouse models of mammary tumor progression.

Accumulation of fibroblasts is a phenomenon that significantly correlates with formation of aggressive cancers. While studies have shown that the TGF-ß signaling pathway is an important regulator of fibroblast activation, the functional contribution of TGF-ß signaling in fibroblasts during multi-step tumor progression remains largely unclear. In previous studies, we used a sub-renal capsule transplantation model to demonstrate that homozygous knockout of the Tgfbr2 gene (Tgbr2(FspKO)) enhanced mammary tumor growth and metastasis. Here, we show for the first time a significant role for loss of one Tgfbr2 allele during multi-step mammary tumor progression. Heterozygous deletion of Tgfbr2 in stromal cells in MMTV-PyVmT transgenic mice (PyVmT/Tgfbr2(hetFspKO) mice) resulted in earlier tumor formation and increased stromal cell accumulation. In contrast to previous studies of Tgbr2(FspKO) fibroblasts, Tgfbr2(hetFspKO) fibroblasts did not significantly increase tumor growth, but enhanced lung metastasis in PyVmT transgenic mice and in co-transplantation studies with PyVmT mammary carcinoma cells. Furthermore, Tgfbr2(hetFspKO) fibroblasts enhanced mammary carcinoma cell invasiveness associated with expression of inflammatory cytokines including CXCL12 and CCL2. Analyses of Tgbr2(FspKO) and Tgfbr2(hetFspKO) fibroblasts revealed differences in the expression of factors associated with metastatic spread, indicating potential differences in the mechanism of action between homozygous and heterozygous deletion of Tgfbr2 in stromal cells. In summary, these studies demonstrate for the first time that loss of one Tgfbr2 allele in fibroblasts enhances mammary metastases in a multi-step model of tumor progression, and demonstrate the importance of clarifying the functional contribution of genetic alterations in stromal cells in breast cancer progression.

RNA-binding protein LIN28 is a marker for primary extragonadal germ cell tumors: an immunohistochemical study of 131 cases.

LIN28 has been shown to have an important role in primordial germ cell development and malignant transformation of germ cells in mouse. In this study, we examined the immunohistochemical profile of LIN28 in 131 primary human extragonadal germ cell tumors (central nervous system (CNS) 76, mediastinum 17, sacrococcygeal region 30, pelvis 3, vagina 2, liver 1, omentum 1, and retroperitoneum 1), including the following tumors and/or components: 57 seminomas/germinomas, 10 embryonal carcinomas, 74 yolk sac tumors, 6 choriocarcinomas, 15 mature, and 13 immature teratomas. We compared LIN28 with SALL4 to assess its diagnostic value. To determine its specificity, we examined LIN28 in 406 extragonadal-non-germ cell tumors (103 carcinomas, 91 sarcomas, 9 melanomas, 12 mesotheliomas, 83 lymphomas, 9 plasmacytomas, 82 CNS tumors, and 17 thymic epithelial tumors). The staining was semi-quantitatively scored as 0 (no cell stained), 1+ (0-30%), 2+ (31-60%), 3+ (61-90%), and 4+ (>90%). LIN28 staining was seen in all seminomas/germinomas (3+ in 1 and 4+ in 56), embryonal carcinomas (4+ in all 10), and yolk sac tumors (3+ in 3 and 4+ in 71). Variable LIN28 staining was seen in 5 of 6 choriocarcinomas (1+ to 4+), 8 of 13 immature teratomas (1+ to 2+ in immature elements), and in 1 of 15 mature teratomas (1+). Only 11 of 406 non-germ cell tumors showed 1+ LIN28 staining. Therefore, LIN28 is a sensitive (100% sensitivity) marker for primary extragonadal seminomas/germinomas, embryonal carcinomas, and yolk sac tumors with high specificity. Compared with SALL4, LIN28 demonstrated a similar level of diagnostic sensitivity for seminomas/germinomas and embryonal carcinomas. For primary extragonadal yolk sac tumors, although SALL4 stained all tumors (1+ in 1, 2+ in 2, 3+ in 10, and 4+ in 61), LIN28 stained more tumor cells (mean 95 vs 90%, P = 0.03) and was therefore more sensitive. For primary extragonadal yolk sac tumors, combining LIN28 and SALL4 can achieve a higher diagnostic sensitivity than either alone.

Intramedullary spinal immature teratoma: resolution of quadriplegia following resection in a 4-week-old infant.

Intramedullary spinal cord teratomas are rare entities in infants. Management of these lesions is primarily surgical, with outcome dependent on rapid surgical decompression and complete gross-total tumor resection. The lesions are typically of the mature type, with immature teratomas displaying unique pathological features. The authors report a case of an extensive intramedullary immature teratoma in an infant with resolution of quadriplegia following gross-total radical resection. At the 1-year follow-up, there was radiographic evidence of tumor, and surgical reexploration yielded portions of immature teratoma and extensive gliosis.

Delayed cerebral radiation necrosis following treatment for a plasmacytoma of the skull.

BACKGROUND: Cerebral radiation necrosis is a relatively common complication of radiation therapy for intracranial malignancies which can also rarely be encountered after radiation of extracranial lesions of the head and neck. We present the first reported case of cerebral radiation necrosis in a patient who underwent radiation therapy for a plasmacytoma of the skull. CASE DESCRIPTION: A 68-year-old male with multiple myeloma presented with an enhancing right frontal mass, 8 years after receiving radiation therapy for a plasmacytoma of the left frontal skull. The patient underwent a diagnostic and therapeutic craniotomy for a presumed neoplastic lesion. The pathologic diagnosis made in this case was delayed radiation necrosis. The patient was followed for over a year during which this process continued to evolve before the ultimate resolution of his clinical symptoms and radiographic abnormality. CONCLUSION: This case highlights the importance of considering radiation necrosis in the differential diagnosis of any patient with an intracranial mass and a history of radiation for an extracranial head and neck malignancy, regardless of timing and laterality. This case also provides unique insights into the ongoing debate regarding the role of the aberrant immune response in the pathogenesis of delayed cerebral radiation necrosis.

Gliomatosis cerebri: report of 3 cases.

Gliomatosis cerebri is an uncommon glial neoplasm that is exceedingly rare in children and difficult to diagnose. The authors describe the presentation and diagnosis of GC in 3 children ages 12, 14, and 16 years. These children exhibited signs and symptoms of increased intracranial pressure as well as other vague or site specific neurological signs. Because clinical presentation, CSF analysis, and neuroimaging were nonspecific, a stereotactic biopsy to obtain tissue for pathological review was ultimately necessary to confirm the diagnosis. These pediatric cases underscore the limitations of relying solely on clinical presentation and neuroimaging and call to attention the essential role of neurosurgical intervention. The authors emphasize the need to maintain gliomatosis cerebri in the differential diagnosis of children presenting with diffuse neurological signs and MR imaging evidence of widespread, infiltrative lesions.

Pediatric gliomatosis cerebri mimicking acute disseminated encephalomyelitis.

Gliomatosis cerebri (GC) is a diffuse infiltrating glial neoplasm of astrocytic origin. GC in children is rare and difficult to diagnose, often presenting with a variety of signs and symptoms that may mimic encephalitis. We discuss here the presentation and diagnosis of GC in 2 children who were initially suspected to have acute disseminating encephalomyelitis. In this report we underscore the limitations of relying on clinical presentation and neuroimaging as well as the essential role of pathologic evaluation for the diagnosis of GC in children.

Activation of the Hedgehog pathway in pilocytic astrocytomas.

Pilocytic astrocytoma is commonly viewed as a benign lesion. However, disease onset is most prevalent in the first two decades of life, and children are often left with residual or recurrent disease and significant morbidity. The Hedgehog (Hh) pathway regulates the growth of higher WHO grade gliomas, and in this study, we have evaluated the activation and operational status of this regulatory pathway in pilocytic astrocytomas. Expression levels of the Hh pathway transcriptional target PTCH were elevated in 45% of tumor specimens analyzed (ages 1-22 years) and correlated inversely with patient age. Evaluation of a tissue array revealed oligodendroglioma-like features, pilomyxoid features, infiltration, and necrosis more commonly in specimens from younger patients (below the median patient age of 10 years). Immunohistochemical staining for the Hh pathway components PTCH and GLI1 and the proliferation marker Ki67 demonstrated that patients diagnosed before the age of 10 had higher staining indices than those diagnosed after the age of 10. A significant correlation between Ki67 and PTCH and GLI1 staining indices was measured, and 86% of Ki67-positive cells also expressed PTCH. The operational status of the Hh pathway was confirmed in primary cell culture and could be modulated in a manner consistent with a ligand-dependent mechanism. Taken together, these findings suggest that Hh pathway activation is common in pediatric pilocytic astrocytomas and may be associated with younger age at diagnosis and tumor growth.