Molecular genetics of meningiomas: from basic research to potential clinical applications

Meningioma of the cerebellopontine angle in identical twins: a case report

Meningiomas in identical twins are extremely rare. To our knowledge, only one previous report of meningiomas in identical twins has been published. We present identical twin sisters with meningiomas. The tumors were located at a similar, but not a common, position (the cerebellopontine angle) in both twins. Histologically, both tumors were diagnosed as meningothelial meningiomas with an angiomatous component. Immunohistochemically, the Ki-67 indices in the two cases were 1.0 and 1.1, and the p53 positive rates were 0.2 and 0.9. The specimens in both cases were reactive to neurofibromin 2 (NF2). A comparative genomic hybridization (CGH) assay revealed an aberration in the long arm of chromosome X, but no aberrations in the long arm of chromosome 22 in either case. These results strongly suggest that genetic aberrations other than NF2 are associated with tumorigenesis in some types of sporadic meningiomas.

A study of meningiomas in South Africa: investigating a correlation between clinical presentation, histopathology and genetic markers

OBJECTIVE

To determine whether there are certain genetic markers which correlate with particular clinical characteristics of meningiomas including multiplicity, recurrence and calvarial erosion.

METHODS

Thirty-eight South African-born patients with meningiomas were recruited for this study. At surgery, blood and tumour specimens were obtained for histopathological, cytogenetic and molecular analysis. Loss of heterozygosity (LOH) on chromosomes 1p and 22q were investigated and the NF2 gene on 22q12.2 was screened for disease-causing mutations.

RESULTS

The commonest tumour locations were convexity (25%) and parasagittal (21%). The histology results showed that 86.8% of the patients had Grade I tumours and the remainder had Grade II tumours. A pathogenic nonsense mutation, R341X in the NF2 gene was found in only one patient. LOH on each of chromosomes 1p and 22q was observed in 44.7% of patients, but in different individuals. Significant associations were found between having specific tumour characteristics and both male gender (p-value = 0.0059) and 22q LOH (p-value = 0.0425). We estimated that having 22q LOH makes an individual approximately four times more likely to develop a tumour that exhibits multiplicity, recurrence or calvarial erosion (OR = 4.8; 95% CI: 1.2-23.4). Adjusting for gender strengthened this effect (OR = 6.1; 95% CI: 1.1-48.7).

CONCLUSIONS

Our data indicate that male patients and patients with a meningioma that has 22q LOH are more likely to develop tumours exhibiting multiplicity, recurrence or calvarial erosion. We recommend that this subset of patients should be followed up more closely. Further study is needed to determine the benefit of adjuvant radiation therapy in this scenario.

Intracranial meningioma in a patient with osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a heritable disorder characterized mainly by connective tissue manifestations. In dinstinct cases, several neurological features have also been described. A 46-year-old male with a known family history of OI type I presented with progressive gait disturbances and diminished muscle strength. Brain MRI scans revealed an infiltrative intracranial mass occupying both frontoparietal lobes. The patient underwent surgical intervention. The histological diagnosis was an atypical (Grade II) meningioma. The bony parts demonstrated a mixture of osseous defects due to OI and infiltration by the tumor. At one-year follow up the patient′s muscle power partially returned while repeat MRI scans were negative for tumor recurrence.

Methylation-specific multiplex ligation-dependent probe amplification in meningiomas

Genomic loss and promotor methylation contribute to inactivation of tumor suppressor genes (TSGs). Methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) is a relatively new method for simultaneous detection of both these alterations. Here, we apply MS-MLPA to a series of 15 meningiomas of different WHO grades. The two MS-MLPA probe sets used detect copy number changes in 55 unselected TSGs and promotor methylation in a subset of 36 of these genes. Our findings concerning genomic deletions are concordant with previously published studies using alternative techniques. The number of aberrations identified per tumor increased with histopathologically determined grading. The most frequent single event was deletion of the von Hippel-Lindau (VHL) gene in 12 of the 15 tumors. Moreover, VHL deletion status was associated with presence/absence of peritumoral edema. Methylation was rare, being observed in only four tumors and in each case restricted to a single gene. We conclude that a meningioma-specific MS-MLPA probe set would be a valuable tool for both research and diagnostic approaches in these tumors.

Hitting a moving target: evolution of a treatment paradigm for atypical meningiomas amid changing diagnostic criteria

OBJECT

The World Health Organization (WHO) reclassified atypical meningiomas in 2000, creating a more clear and broadly accepted definition. In this paper, the authors evaluated the pathological and clinical transition period for atypical meningiomas according to the implementation of the new WHO grading system at their institution.

METHODS

A total of 471 meningiomas occurring in 440 patients between 1994 and 2006 were retrospectively reviewed to determine changes in diagnostic rates, postoperative treatment trends, and early outcomes.

RESULTS

Between 1994 and 2000, the incidence of the atypical meningiomas ranged from 0 to 3/year, or 4.4% of the meningiomas detected during the entire period. After 2002, the annual percentage of atypical meningiomas rose over a 2-year period, leveling off at between 32.7 and 35.5% between 2004 and 2006. The authors also found a recent trend toward increased use of adjuvant radiation therapy for incompletely resected atypical meningiomas. Prior to 2003, 18.7% were treated with this therapy; after 2003, 34.4% of lesions received this treatment. Incompletely resected tumors were treated with some form of radiation 76% of the time. In cases of complete resection, most patients were not given adjuvant therapy but were expectantly managed by close monitoring using serial imaging and by receiving immediate treatment for tumor recurrence. The overall recurrence rate for expectantly managed tumors was 9% over 28.2 months, and 75% of recurrences responded to delayed radiation therapy.

CONCLUSIONS

The authors documented a significant change in the proportion of meningiomas designated as atypical during a transition period from 2002 to 2004, and propose a conservative strategy for the use of radiation therapy in atypical meningiomas.

Review of meningioma histopathology

✓The histological appearance of a meningioma is an important predictor of tumor behavior and is frequently a factor in decisions concerning therapy. The relationship between histological features and prognosis is formalized in grading schemes such as those published by the World Health Organization (WHO), most recently in 2007. Although the latest edition is an improvement over previous grading schemes, the WHO scheme still fails to fully address a variety of important issues regarding the relationship between meningioma histological characteristics and behavior. In particular, routine histological examination fails to identify the subset of Grade I tumors that behave aggressively. Because of this, many additional prognostic markers that require immunohistochemical, cytogenetic, or molecular techniques to evaluate are under investigation. Only one, immunohistochemistry for the proliferation marker, Ki 67 (MIB-1), is used routinely and it has only limited utility. It is hoped that an understanding of the genetic changes that underlie tumor progression will improve healthcare professionals' ability to predict the behavior of meningiomas.