Glial neoplasms: dynamic contrast-enhanced T2*-weighted MR imaging.

PURPOSE: To evaluate the role of T2*-weighted echo-planar perfusion imaging by using a first-pass gadopentetate dimeglumine technique to determine the association of magnetic resonance (MR) imaging-derived cerebral blood volume (CBV) maps with histopathologic grading of astrocytomas and to improve the accuracy of targeting of stereotactic biopsy. MATERIALS AND METHODS: MR imaging was performed in 29 patients by using a first-pass gadopentetate dimeglumine T2*-weighted echo-planar perfusion sequence followed by conventional imaging. The perfusion data were processed to obtain a color map of relative regional CBV. This information formed the basis for targeting the stereotactic biopsy. Relative CBV values were computed with a nondiffusible tracer model. The relative CBV of lesions was expressed as a percentage of the relative CBV of normal white matter. The maximum relative CBV of each lesion was correlated with the histopathologic grading of astrocytomas obtained from samples from stereotactic biopsy or volumetric resection. RESULTS: The maximum relative CBV in high-grade astrocytomas (n = 26) varied from 1.73 to 13.7, with a mean of 5.07 +/- 2.79 (+/- SD), and in the low-grade cohort (n = 3) varied from 0.92 to 2.19, with a mean of 1.44 +/- 0.68. This difference in relative CBV was statistically significant (P < .001; Student t test). CONCLUSION: Echo-planar perfusion imaging is useful in the preoperative assessment of tumor grade and in providing diagnostic information not available with conventional MR imaging. The areas of perfusion abnormality are invaluable in the precise targeting of the stereotactic biopsy.     

MicroRNA profiling in pediatric pilocytic astrocytoma reveals biologically relevant targets,including PBX3, NFIB,and METAP2

Pilocytic astrocytoma (PA) is a World Health Organization grade I glioma that occurs most commonly in children and young adults. Specific genetic alterations have been described in PA, but the pathogenesis remains poorly understood. We studied microRNA (miRNA) alterations in a large cohort of patients with PA. A total of 43 PA, including 35 sporadic grade I PA, 4 neurofibromatosis-1 (NF1)–associated PA, and 4 PA with pilomyxoid features, as well as 5 nonneoplastic brain controls were examined. BRAF fusion status was assessed in most cases. RNA was examined using the Agilent Human miRNA Microarray V3 platform. Expression of miRNA subsets was validated using quantitative real-time PCR (qRT-PCR) with Taqman probes. Validation of predicted protein targets was performed on tissue microarrays with the use of immunohistochemistry. We identified a subset of miRNAs that were differentially expressed in pediatric PAs versus normal brain tissue: 13 miRNAs were underexpressed, and 20 miRNAs were overexpressed in tumors. Differences were validated by qRT-PCR in a subset, with mean fold change in tumor versus brain of -17 (miR-124), -15 (miR-129), and 19.8 (miR-21). Searching for predicted protein targets in Targetscan, we identified a number of known and putative oncogenes that were predicted targets of miRNA sets relatively underexpressed in PA. Predicted targets with increased expression at the mRNA and/or protein level in PA included PBX3, METAP2, and NFIB. A unique miRNA profile exists in PA, compared with brain tissue. These miRNAs and their targets may play a role in the pathogenesis of PA.     

Angiographic abnormalities in progressive multifocal leukoencephalopathy: an explanation based on neuropathologic findings

BACKGROUND AND PURPOSE: Progressive multifocal leukoencephalopathy (PML) is typically occult at angiography and fails to enhance on MR images. After observing angiographic abnormalities characterized by arteriovenous shunting and pathologic parenchymal blush in patients with AIDS-related PML, often in the absence of contrast enhancement on MR images, we hypothesized that there might be distinct changes in the cerebral microvasculature that account for the reduction in vascular transit time (arteriovenous shunting) in the absence of blood-brain barrier dysfunction. METHODS: The imaging studies and neuropathologic specimens of six patients with biopsy-proved PML were reviewed retrospectively. In all patients contrast-enhanced MR imaging and CT, followed by cerebral angiography, were performed before stereotactically directed biopsy. The angiograms were evaluated for the presence of vascular displacement, pathologic parenchymal blush, arteriovenous shunting, and neovascularity. The CT and MR studies were reviewed for the presence of enhancement of the PML lesions. Biopsy specimens were examined for the presence of necrosis, perivascular inflammation, and neovascularity. RESULTS: All patients had oligodendrocytic intranuclear inclusions diagnostic of PML, together with perivascular inflammation and neovascularity to a varying extent; no other neuropathologic processes were identified. Angiographic abnormalities, characterized by a pathologic parenchymal blush and arteriovenous shunting, were identified in four of the six patients. In only one of these cases, however, was abnormal enhancement identified on cross-sectional imaging studies (MR and CT), and this patient had florid perivascular inflammatory infiltrates histologically. CONCLUSION: The pathologic parenchymal blush and arteriovenous shunting seen angiographically in some patients with PML reflect small-vessel proliferation and perivascular inflammatory changes incited by the presence of the JC virus in infected oligodendrocytes.     

Growth factor receptor tyrosine kinases: cell adhesion kinase family suggests a novel signaling mechanism in cancer

Future advances in oncology will increasingly rely on an understanding of the molecular biology of tumorigenesis. Recent laboratory work has elucidated many molecular events contributing to tumor formation. In particular, the signaling pathways for growth factors have been implicated in the genesis and maintenance of several human tumors (1). Growth factor autocrine and paracrine stimulatory loops promote tumor proliferation and angiogenesis. A family of structurally related growth factor receptors, the receptor tyrosine kinases (RTKs), are particularly relevant to cancer biology. This large family includes the receptors for epidermal growth factor, the platelet-derived growth factor, the fibroblast growth factor, the insulin-like growth factor, the neurotrophins related to nerve growth factor, the vascular endothelial growth factor, the ephrins, and several receptors for which no growth factor ligand has been identified. Several of these receptor molecules and their growth factor ligands are preferentially expressed in the embryo and are thought to play a central role in regulating the determination of cell fate during development. Moreover, the overexpression or mutation of genes encoding these receptors can be oncogenic. Researchers believe that some receptors in this family, those that have been shown to be overexpressed or mutated in human tumors, contribute to cancer formation.     

Neurolisteriosis presenting as recurrent transient ischemic attacks

An elderly man experienced recurrent transient episodes of right arm weakness and expressive aphasia. He was initially treated with aspirin and then with coumadin. Thirteen days after initial presentation, he became febrile and had signs of meningitis. The illness progressed relentlessly to death 9 weeks after admission to the hospital. Necropsy showed prominent meningitis with vasculitis extending into the left frontal lobe. Polymerase chain reaction identified the organism as Listeria monocytogenes.     

March 2002: 28-year-old woman with neck and back pain

Following a car accident a 28-year-old female, complained of a sharp pain of the anterior and posterior base of the neck on expiration and with exertion. Subsequently, she noticed a feeling of discomfort in her back when lifting her arm above her head. Imaging studies revealed a tumor mass involving the third intercostal nerve on the right side of T2. The differential diagnosis included neurofibroma and neurilemmoma. This was followed annually and five years later an increase in size warranted a transthoracic, transpleural removal en bloc of this lesion. At surgery, a 3 cm soft tissue tumor engulfed the third intercostal nerve and extended into the third intervertebral foramen where the proximal part of the nerve root was enlarged. The right third intercostal nerve was dissected and removed along with the tumor, after negative nerve stimulation. Histopathological examination showed multiple enlarged coalescent lymphoid follicles with an onion skin appearance of tight concentric layering of small, uniform mature lymphocytes at the periphery, arranged in a targetoid fashion with broad mantle zones and relatively small germinal centers. The germinal centers of variable size included hyalinized blood vessels. Lollipop follicles were seen. The interfollicular stroma showed numerous hyperplastic collagenized capillaries within an inflammatory background. However, the perinodal soft tissue was replaced by numerous inflammatory cells, primarily lymphocytes. The final diagnosis was Castleman's disease, hyaline vascular type. Castleman's disease can mimic various tumors and because Castleman's disease is a rare reactive entity, its diagnosis is generally overlooked by radiologists and clinicians. It is likely that this mass arose from one of the posterior intercostal lymph nodes, situated in the paravertebral region, however the capsule was not readily seen and the sinuses were not apparent. Almost all previous cases of Castleman's disease, hyaline vascular type were described in the anterior mediastinum. Hyaline vascular Castleman's disease usually does not invade and replace neighboring structures. This case is unique because of its location and the local invasion of adjacent structures.     

The combination of ionizing radiation and peripheral vaccination produces long-term survival of mice bearing established invasive GL261 gliomas.

PURPOSE: High-grade glioma treatment includes ionizing radiation therapy. The high invasiveness of glioma cells precludes their eradication and is responsible for the dismal prognosis. Recently, we reported the down-regulation of MHC class I (MHC-I) products in invading tumor cells in human and mouse GL261 gliomas. Here, we tested the hypothesis that whole-brain radiotherapy (WBRT) up-regulates MHC-I expression on GL261 tumors and enhances the effectiveness of immunotherapy. EXPERIMENTAL DESIGN: MHC-I molecule expression on GL261 cells was analyzed in vitro and in vivo by flow cytometry and immunohistochemistry, respectively. To test the response of established GL261 gliomas to treatment, mice with measurable (at CT imaging) brain tumors were randomly assigned to four groups receiving (a) no treatment, (b) WBRT in two fractions of 4 Gy, (c) vaccination with irradiated GL261 cells secreting granulocyte-macrophage colony-stimulating factor, or (d) WBRT and vaccination. Endpoints were tumor response and survival. RESULTS: An ionizing radiation dose of 4 Gy maximally up-regulated MHC-I molecules on GL261 cells in vitro. In vivo, WBRT induced the expression of the beta2-microglobulin light chain subunit of the MHC class I complex on glioma cells invading normal brain and increased CD4+ and CD8+ T cell infiltration. However, the survival advantage obtained with WBRT or vaccination alone was minimal. In contrast, WBRT in combination with vaccination increased long-term survival to 40% to 80%, compared with 0% to 10% in the other groups (P < 0.002). Surviving animals showed antitumor immunity by rejecting challenge tumors. CONCLUSION: Ionizing radiation can be successfully combined with peripheral vaccination for the treatment of established high-grade gliomas.