Chromosomal involvement secondary to -22 in human meningiomas

Histologic and Cytogenetic Patterns in Benign, Atypical, and Malignant Meningiomas

Atypical meningiomas comprise an intermediate category of meningeal neoplasmas with some microscopic features of aggressivity and a capacity for recurrence. We present a clin ical, morphologic, and cytogenetic study of 15 meningiomas. Morphologic and cytogenetic analysis suggested the existence of morphologically typical meningiomas with normal karyotype or monosomy 22 and morphologically atypical meningiomas, with increasing chromosomal abnormalities (complex karyotype) between these two types. Present results suggest the existence of a third type of morphologically typical meningioma that lacks a phenotypical aggressivity but has a complex karyotype. These genotypical characteristics may be related to the aggressivity of these neoplasms. Int J Surg Pathol 2(4):301-310, 1995

Three gangliogliomas: results of GTG-banding, SKY, genome-wide high resolution SNP-array, gene expression and review of the literature

According to the World Health Organization gangliogliomas are classified as well-differentiated and slowly growing neuroepithelial tumors, composed of neoplastic mature ganglion and glial cells. It is the most frequent tumor entity observed in patients with long-term epilepsy. Comprehensive cytogenetic and molecular cytogenetic data including high-resolution genomic profiling (single nucleotide polymorphism (SNP)-array) of gangliogliomas are scarce but necessary for a better oncological understanding of this tumor entity. For a detailed characterization at the single cell and cell population levels, we analyzed genomic alterations of three gangliogliomas using trypsin-Giemsa banding (GTG-banding) and by spectral karyotyping (SKY) in combination with SNP-array and gene expression array experiments. By GTG and SKY, we could confirm frequently detected chromosomal aberrations (losses within chromosomes 10, 13 and 22; gains within chromosomes 5, 7, 8 and 12), and identify so far unknown genetic aberrations like the unbalanced non-reciprocal translocation t(1;18)(q21;q21). Interestingly, we report on the second so far detected ganglioglioma with ring chromosome 1. Analyses of SNP-array data from two of the tumors and respective germline DNA (peripheral blood) identified few small gains and losses and a number of copy-neutral regions with loss of heterozygosity (LOH) in germline and in tumor tissue. In comparison to germline DNA, tumor tissues did not show substantial regions with significant loss or gain or with newly developed LOH. Gene expression analyses of tumor-specific genes revealed similarities in the profile of the analyzed samples regarding different relevant pathways. Taken together, we describe overlapping but also distinct and novel genetic aberrations of three gangliogliomas.

Genomic deletions at 1p and 14q are associated with an abnormal cDNA microarray gene expression pattern in meningiomas but not in schwannomas

The molecular pathology of meningiomas and shwannomas involve the inactivation of the NF2 gene to generate grade I tumors. Genomic losses at 1p and 14q are observed in both neoplasms, although more frequently in meningiomas. The inactivation of unidentified genes located in these regions appears associated with tumor progression in meningiomas, but no clues to its molecular/clinical meaning are available in schwannomas. Recent microarray gene expression studies have demonstrated the existence of molecular subgroups in both entities. In the present study, we correlated the presence of genomic deletions at 1p, 14q, and 22q with the expression patterns of 96 tumor-related genes obtained by cDNA low-density microarrays in a series of 65 tumors including 42 meningiomas and 23 schwannomas. Two expression pattern groups were identified by cDNA mycroarray analysis when compared to the expression pattern in normal control RNA in both meningiomas and schwannomas, each one with patterns similar and different from the normal control. Meningioma and schwannoma subgroups differed in the expression of 38 and 16 genes, respectively. Using MLPA and microsatellites, we identified genomic losses at 1p, 14q, and 22q at nonrandom frequencies (12.5-69%) in meningiomas and schwannomas. Losses at 22q were almost equally frequent in both molecular expression subgroups in both neoplasms. However, deletions at 1p and 14q accumulated in meningiomas with a gene expression pattern different from the normal pattern, whereas the inverse situation occurred in schwannomas. Those anomalies characterized the schwannomas with expression pattern similar to the normal control. These findings suggest that deletions at 1p and 14q enhance the development of an abnormal tumor-related gene expression pattern in meningiomas, but this fact is not corroborated in schwannomas.

Molecular cytogenetic analysis in the study of brain tumors: findings and applications

Classic cytogenetics has evolved from black and white to technicolor images of chromosomes as a result of advances in fluorescence in situ hybridization (FISH) techniques, and is now called molecular cytogenetics. Improvements in the quality and diversity of probes suitable for FISH, coupled with advances in computerized image analysis, now permit the genome or tissue of interest to be analyzed in detail on a glass slide. It is evident that the growing list of options for cytogenetic analysis has improved the understanding of chromosomal changes in disease initiation, progression, and response to treatment. The contributions of classic and molecular cytogenetics to the study of brain tumors have provided scientists and clinicians alike with new avenues for investigation. In this review the authors summarize the contributions of molecular cytogenetics to the study of brain tumors, encompassing the findings of classic cytogenetics, interphase- and metaphase-based FISH studies, spectral karyotyping, and metaphase- and array-based comparative genomic hybridization. In addition, this review also details the role of molecular cytogenetic techniques in other aspects of understanding the pathogenesis of brain tumors, including xenograft, cancer stem cell, and telomere length studies.

Genetic and epigenetic alteration of theNF2gene in sporadic meningiomas

The role of the NF2 gene in the development of meningiomas has recently been documented; inactivating mutations plus allelic loss at 22q, the site of this gene (at 22q12), have been identified in both sporadic and neurofibromatosis type 2-associated tumors. Although epigenetic inactivation through aberrant CpG island methylation of the NF2 5' flanking region has been documented in schwannoma (another NF2-associated neoplasm), data on participation of this epigenetic modification in meningiomas are not yet widely available. Using methylation-specific PCR (MSP) plus sequencing, we assessed the presence of aberrant promoter NF2 methylation in a series of 88 meningiomas (61 grade I, 24 grade II, and 3 grade III), in which the allelic constitution at 22q and the NF2 mutational status also were determined by RFLP/microsatellite and PCR-SSCP analyses. Chromosome 22 allelic loss, NF2 gene mutation, and aberrant NF2 promoter methylation were detected in 49%, 24%, and 26% of cases, respectively. Aberrant NF2 methylation with loss of heterozygosity (LOH) at 22q was found in five cases, and aberrant methylation with NF2 mutation in another; LOH 22q and the mutation were found in 16 samples. The aberrant methylation of the NF2 gene also was the sole alteration in 15 samples, most of which were from grade I tumors. These results indicate that aberrant NF2 hypermethylation may participate in the development of a significant proportion of sporadic meningiomas, primarily those of grade I.

Meningioma: Un modelo de evolución citogenética en la iniciación y progresión tumoral

Meningiomas are tumors of the central nervous system with a great morphological heterogeneity. They are generally benign, and have the capacity to progress to a higher histological grade (atypical and anaplastic), which is associated with an increase in biological aggressivity and/or capacity to recur. Citogenetically this evolution is characterized by total or partial monosomy 22 in the early phase, continued by numerical and structural changes during tumor progression. In this study, we present a review of 85 cases of meningiomas: 43 benign, 28 atypical and 14 anaplastic. We study the clinical and histopathological features, and their correlation with cytogenetie abnormalities present in these tumors. Numerical aberrations such as monosomy of chromosome 10, 14 and 18, and structural abnormalities such as deletions on 1p are directly associated with a higher agressivity of tumors. An association of aberatons on 1p and chromosome 14 are more commonly found in atypical and anaplastic meningiomas. These facts imply that the presence of complex karyotypes progressively increases from grade I to grade III meningiomas. Furthermore, these karyotypes are common in recurrent tumors.

Translocation (1;19)(q21;q13.3) is a recurrent reciprocal translocation in meningioma

Benign meningiomas are characterized by a normal karyotype or loss of all or part of chromosome 22. Histologically higher grade tumors are typically characterized by a pattern of increasing chromosome loss and instability. This characteristic pattern of unbalanced chromosome aberrations is punctuated in the literature by several intriguing reports of a reciprocal t(1;19)(q21;q13.3) as the sole cytogenetic aberration. We report a third case showing the t(1;19)(q21;q13.3) with additional unstable secondary aberrations of a dic(18;22)(p11;p11) and telomeric fusions.

Loss of chromosome 22 and absence of NF2 gene mutation in a case of multiple meningiomas

Multiple meningiomas are rare, and only 13 cases have been subjected to molecular genetic analysis to detect mutations of the tumor-suppressor gene neurofibromatosis type 2 (NF2) located on chromosome 22. Most of these cases display NF2 gene mutations parallel to loss of the chromosome 22 homolog, indicating that inactivation of this gene may represent an early event in the development of multiple meningiomas. We report a case of a 61-year-old woman who developed multiple (dorsal and intracranial) meningiomas. Cytogenetic and molecular genetic studies demonstrated the loss of a copy of chromosome 22 in the 5 meningiomas studied and the absence of NF2 gene mutations in 4 of those available for this molecular analysis. These findings, together with similar data from 2 previously reported cases, suggest the participation of a tumor-suppressor gene other than NF2 on chromosome 22 in the pathogenesis of a subgroup of multiple meningiomas.

Meningioma: a cytogenetic model of a complex benign human tumor, including data on 394 karyotyped cases

Meningioma is the most frequent tumor of neuroectodermal origin in humans. It is usually benign. Only a minority of cases shows progression to an anaplastic tumor (WHO grade II and III). Meningioma is generally a sporadic tumor. Multiple and familial cases are rare and mostly associated with (hereditary) neurofibromatosis 2 (NF2). Meningiomas show an unexpectedly high recurrence rate. Also, completely removed low-grade tumors can recur. Recurrence and multiplicity are correlated with the formation of a peritumoral edema. On the cytogenetic level, meningioma is the best-studied tumor in humans. Grade I tumors show either uniform monosomy 22 or a diploid karyotype. The majority of high-grade, but only a minority of low-grade, meningiomas show loss of merlin, a cytoskeleton-cytoplasm-linker protein. Merlin is the product of the NF2 gene located on chromosome 22. A second tumor suppressor gene on chromosome 22 has not yet been detected. In contrast to other solid tumors, progression of meningiomas is correlated with increasing hypodiploidy, showing characteristic clonal evolutions that mostly include chromosomes 14, 18, and 19 and, more rarely, 6 and 10. Structural aberrations are infrequent, except for the loss of the short arm of chromosome 1, which appears to be the decisive step for anaplastic growth. Comparative histochemical and molecular cytogenetic studies point to the alkaline phosphatase gene (ALPL, liver-bone-kidney type) located on 1p36.1-->p34 as a candidate tumor suppressor gene. A model is proposed that tries to explain - with a minimum number of essential steps - the origin, progression, infiltration, and recurrence of meningiomas.

Analysis of p73 gene in meningiomas with deletion at 1p

The p73 gene has been mapped to 1p36.33, a chromosome region that is frequently deleted in a wide variety of neoplasms including meningiomas. The protein encoded by p73 shows structural and functional similarities to p53 and may thus represent a candidate tumor suppressor gene. To determine whether p73 is involved in the development of meningiomas, we examined 30 meningioma samples with proven 1p deletion for mutations of p73. Sequence analysis of the entire coding region of the p73 gene revealed previously reported polymorphisms in eight cases. A tumor-specific missense mutation as a result of an A-to-G transition with an Asn204Ser change was found in one meningioma that nevertheless retained the normal allele. These results suggest that if p73 plays a role in meningioma carcinogenesis, it must be in a manner different from the Knudson two-hit model.

Loss of 1p in recurrent meningiomas

Deletion of 1p is associated with histological progression to meningiomas. Detection of this alteration may be a predicting factor for recurrences in this tumor. We present 8 meningiomas from four patients: the original tumor and the first recurrence in one patient, and the first and second recurrences in the other three were studied. We compared results of monosomy 22 and deletion of chromosome 1p with cytogenetic methods and fluorescence in situ hybridization (FISH) analysis obtained from slides of direct preparations, of cultured cells and slides of touch preparations. The cytogenetic study showed normal chromosome 22 and deletion on 1p32 in both samples of one patient; only monosomy 22 in both recurrences in another patient, and normal karyotypes with different non-clonal anomalies in the other tumors. However, with FISH analysis, monosomy 22 in both recurrences of three patients was demonstrated, as well as the loss of 1p in all tumors. These results were more evident in the analysis of direct and touch preparations than in those of cultured cells.

High-resolution analysis of chromosome arm 1p alterations in meningioma

Loss of heterozygosity (LOH) for loci on chromosome arm 1p is a relatively common event in human meningioma, and this anomaly has been proposed to be associated with the development of grade II or grade III forms (atypical and anaplastic meningiomas). Nevertheless, the limited data available do not allow the establishment of the frequency and the extent of the affected 1p regions. To determine the status of chromosome 1p in meningiomas, we have performed a comprehensive analysis of LOH on 1p in 100 meningiomas using a high density of 1p-marker loci. Allelic loss was found in 35% of tumors, most corresponding to nontypical meningiomas that also displayed losses for loci on chromosome 22. Although some tumors displayed complex rearrangements leading to distinct 1p deletions, the patterns of loss indicated two main target regions: 1p36 and 1p34-p32, which represent the most frequently involved regions, whereas 1p22 and 1p21.1-1p13 regions appeared deleted in some tumors. These results suggest that there may be several putative tumor suppressor genes on 1p, the inactivation of which may be important in the pathogenesis of meningiomas, as well as in other tumor types.

A case of papillary meningioma with a t(1;4)(q44;q21)

We report the results of cytogenetic analyses of three cases of meningiomas. The first case, a papillary meningioma, showed only one cytogenetic abnormality, 46,XX,t(1;4)(q44;q21). In contrast, the other two benign fibroblastic meningiomas showed loss of chromosome 22. Loss and/or rearrangement of chromosomes other than chromosome 22 appears to be associated with a more aggressive clinical course. It is suggested that a sole cytogenetic abnormality with a normal chromosome 22 indicates an atypical nature of meningioma.

Histopathological and cytogenetic findings in benign, atypical and anaplastic human meningiomas: a study of 60 tumors

Meningiomas may display benign (Grade I), atypical (Grade II) and anaplastic (Grade III) histopathological findings. The cytogenetic studies strongly suggest that secondary changes (moreover loss of chromosome 22) appear to be associated with more atypical features and with greater clinical aggressivity. We studied 60 tumors from 52 patients. Histopathological features such as nuclear pleomorphism, nucleolar prominence, mitosis, necrosis, cellular density, PCNA labeling index, and karyotype have been evaluated. Nuclear pleomorphism and nucleolar prominence showed a progressive increase in Grades I-III. Multifocal micronecrosis was considered a criterion of malignancy. A significant correlation was observed between PCNA-LI, mitotic index and grades. Complex karyotypes increased progressively: benign (34% of cases), atypical (45% of cases) and anaplastic (70% of cases). The most common numerical alterations were losses of chromosomes 10, 14, 18 and 22. The chromosomes most often involved in structural anomalies were: 1, 4, 7, 14 and 22. Telomeric associations was present in four cases and double minutes in two cases. Prognostic criteria for these tumors have been analyzed on the basis of these data.

NF2 gene mutations and allelic status of 1p, 14q and 22q in sporadic meningiomas

Formation of meningiomas and their progression to malignancy may be a multi-step process, implying accumulation of genetic mutations at specific loci. To determine the relationship between early NF2 gene inactivation and the molecular mechanisms that may contribute to meningioma tumor progression, we have performed deletion mapping analysis at chromosomes 1, 14 and 22 in a series of 81 sporadic meningiomas (54 grade I (typical), 25 grade II (atypical) and two grade III (anaplastic)), which were also studied for NF2 gene mutations. Single-strand conformational polymorphism analysis was used to identify 11 mutations in five of the eight exons of the NF2 gene studied. All 11 tumors displayed loss of heterozygosity (LOH) for chromosome 22 markers; this anomaly was also detected in 33 additional tumors. Twenty-nine and 23 cases were characterized by LOH at 1p and 14q, respectively, mostly corresponding to aggressive tumors that also generally displayed LOH 22. All three alterations were detected in association in seven grade II and two grade III meningiomas, corroborating the hypothesis that the formation of aggressive meningiomas follows a multi-step tumor progression model.

Comparative genomic hybridization analysis of genetic alterations associated with malignant progression of meningioma

Little is known about genetic alterations during malignant progression of meningioma. We used comparative genomic hybridization (CGH) in 20 patients (13 with typical, 4 with atypical and 3 with anaplastic meningiomas) to investigate the genetic pathway underlying the development of meningioma. Typical meningiomas displayed only a few genetic changes such as monosomy 22. Anaplastic meningiomas manifested more aberrations than typical meningiomas, frequently exhibiting losses of 1p, 2p, 6q, chromosome 10 and 14q, and gain of 20q, in addition to monosomy 22. The average number of alteration sites in each patient with typical meningioma was significantly less than those in each patient with atypical (p < 0.01) and with anaplastic meningioma (p < 0.05). Anaplastic meningiomas showed the chromosomal changes seen in atypical meningiomas together with other aberrations. These CGH findings suggest that losses of 1p, 2p, 6q, chromosome 10 and 14q, and gain of 20q are genetic changes implicated in the malignant progression of meningioma.

Analysis of genomic alterations in benign, atypical, and anaplastic meningiomas: toward a genetic model of meningioma progression

Nineteen benign [World Health Organization (WHO) grade I; MI], 21 atypical (WHO grade II; MII), and 19 anaplastic (WHO grade III; MIII) sporadic meningiomas were screened for chromosomal imbalances by comparative genomic hybridization (CGH). These data were supplemented by molecular genetic analyses of selected chromosomal regions and genes. With increasing malignancy grade, a marked accumulation of genomic aberrations was observed; i.e., the numbers (mean +/- SEM) of total alterations detected per tumor were 2.9 +/- 0.7 for MI, 9.2 +/- 1.2 for MII, and 13.3 +/- 1.9 for MIII. The most frequent alteration detected in MI was loss on 22q (58%). In MII, aberrations most commonly identified were losses on 1p (76%), 22q (71%), 14q (43%), 18q (43%), 10 (38%), and 6q (33%), as well as gains on 20q (48%), 12q (43%), 15q (43%), 1q (33%), 9q (33%), and 17q (33%). In MIII, most of these alterations were found at similar frequencies. However, an increase in losses on 6q (53%), 10 (68%), and 14q (63%) was observed. In addition, 32% of MIII demonstrated loss on 9p. Homozygous deletions in the CDKN2A gene at 9p21 were found in 4 of 16 MIII (25%). Highly amplified DNA sequences were mapped to 12q13-q15 by CGH in 1 MII. Southern blot analysis of this tumor revealed amplification of CDK4 and MDM2. By CGH, DNA sequences from 17q were found to be amplified in 1 MII and 8 MIII, involving 17q23 in all cases. Despite the high frequency of chromosomal aberrations in the MII and MIII investigated, none of these tumors showed mutations in exons 5-8 of the TP53 gene. On the basis of the most common aberrations identified in the various malignancy grades, a model for the genomic alterations associated with meningioma progression is proposed.

Loss of heterozygosity of chromosome 14q in low- and high-grade meningiomas

Abnormalities of chromosome 22q have been well studied as a major molecular genetic event in meningiomas. Chromosome 14q loss has also been shown to be a common phenomenon. However, only a few studies have reported molecular genetic changes of this chromosome in meningioma. In this study, we examined 41 sporadic meningiomas of different histological subtypes and grades with 15 polymorphic microsatellite markers covering a wide region on chromosome 14q. Overall, 37% (15 of 41) of cases showed loss of heterozygosity for one or more allelic markers. Thirty percent (10 of 33) of benign tumors showed allelic losses, whereas 62.5% (5 of 8) of high-grade meningiomas showed loss of heterozygosity. There were altogether eight cases of partial deletions and seven cases of probable monosomy of 14q. Allelic losses of 14q were also commonly seen in recurrent tumors (3 of 3, 100%), parasagittal tumors (4 of 7, 57%), and tumors with transitional subtype (7 of 14, 50%). Among the tumors with allelic losses of 14q, all except one concurrently showed loss of heterozygosity for markers on 22q by our previous study. Of the eight cases with partial deletions, one showed losses on 14q11.1-31, two showed deletions on 14q24.3-31, three showed losses at 14q32.1-32.2, and the remaining two showed deletions at 14q24.3-32.2. We therefore defined two cluster regions of deletion on chromosome 14q: 14q24.3-31 and 14q32.1-32.2. Our studies suggested that more than one tumor suppressor gene(s) residing on distinct regions of chromosome 14q are important in the development and atypical or anaplastic changes in meningiomas.

Dosimetric and cytogenetic studies of multiple radiation-induced meningiomas for a single patient

No criteria are currently available to determine the spontaneous or radiation-induced origin of a malignant tumor occurring in a previously irradiated area. This study presents the dosimetric and cytogenetic analysis of meningiomas diagnosed in irradiated brain areas from a single patient and a discussion of the karyotypes of spontaneous meningiomas and radiation-induced tumors published in the literature.

The human chromosome 22-located genes and malignancies of the central nervous system

The human chromosome 22 displays an unusual concentration of medically relevant genes, especially gene(s) involved in malignancies of the central nervous system. A full genomic and transcriptional characterization of this autosome will no doubt make a strong impact on the understanding of some of the processes which lead to the development of these tumours.

Cytogenetic analysis of aggressive meningiomas: possible diagnostic and prognostic implications

BACKGROUND

Published karyotypes from aggressive (atypical and malignant) meningiomas are few, but suggest clonal evolution from benign tumors with monosomy 22 to aggressive forms with additional abnormalities. The goal of this study was to identify the most frequent karyotypic abnormalities associated with aggressive histopathology and biologic behavior.

METHODS

Eight intracranial meningiomas exhibiting histologically atypical features at the time of intraoperative diagnosis were chosen for cytogenetic analysis. The study set was comprised entirely of histologically atypical meningiomas. Four were considered malignant; three on the basis of brain invasion and one due to extracranial metastases. None was histologically anaplastic.

RESULTS

Chromosomal abnormalities were demonstrated in 6 cases (75%), 5 of which were complex (63%). Loss of chromosome 22 was identified in two cases, both of which were associated with additional aberrations. Abnormalities most frequently involved chromosomes 1 (63%), 3 (50%), and 6 (63%). Four cases (50%) had dicentric or ring chromosomes. An additional 47 previously reported karyotypes from atypical and malignant meningiomas were reviewed. Comparison with published karyotypes of 200 histologically benign meningiomas served to underscore the increased frequency of complex karyotypes, chromosome 1, 3, and 6 abnormalities, and telomeric associations in the aggressive tumors. Apparently normal karyotypes as well as monosomy 22 alone were more frequently associated with benign, nonatypical histopathology.

CONCLUSIONS

These findings suggest a possible role for cytogenetic analysis in determining the prognosis and perhaps in refining the diagnosis of atypical or aggressive meningiomas. Further studies are necessary to determine the significance of complex karyotypes, chromosome 1, 3, and 6 abnormalities, and telomeric associations, particularly whether they portend a more aggressive clinical course in meningiomas lacking features of histologic atypia.

Cytogenetical findings of recurrent meningiomas. A study of 10 tumors

Cytogenetic analyses of 10 cases of recurrent meningiomas growing in culture between 1-10 days are reported, of which seven showed benign morphology, one atypical, and two, malignant features. Normal karyotypes with nonclonal alterations were found in three cases, one case with only monosomy 22, and complex karyotypes in the remaining six. Four cases were hypodiploid, one pseudodiploid, and one hyperdiploid. The chromosomes most often involved in structural rearrangements were 1, 7, and 14 and the losses were chromosomes 7, 10, 14, 15, 18, and 22. Ring chromosome, dicentrics, double minutes, and association between satellites were found in one case. These complex karyotypes with hypodiploidy, structural rearrangements, and other markers in recurrent meningiomas may indicate aggressive tumor characteristics.

Triple approach for diagnosis and grading of meningiomas: histology, morphometry of Ki-67/Feulgen stainings, and cytogenetics

With regard to meningioma grading and the recently introduced "atypical" meningioma, we evaluated 160 cases retrospectively by conventional histology and image analysis. For that, the cell nuclei were stained with a Ki-67 (MIB1)/Feulgen-method on paraffin sections, thus enabling the assessment of both the Ki-67 proliferation index and nuclear morphometric features, such as tumour cell arrangement, nuclear pleomorphism, and cellularity. It could be demonstrated that the Ki-67 proliferation index is the most important criterion for distinguishing anaplastic meningiomas (WHO "grade" III) (mean Ki-67 index: 11%) from those of common type (WHO "grade" I) (mean Ki-67 index: 0.7%). The parameter for the "relative volume weighted mean nuclear volume" is another valuable morphometric feature. The "atypical" meningioma (WHO "grade" II) which should represent an intermediate category between common type and anaplastic meningiomas is characterized by a mean Ki-67 proliferation index of 2.1%. Common type meningiomas which comprise almost 50% of the cases of this series have a relapse rate of 9%. "Atypical" and anaplastic meningiomas recurred in 29% and 50%, respectively. Since the term "atypical" meningioma is confusing in the context of tumour grading, the term "intermediate type meningioma" is proposed. Furthermore, the results of cytogenetic analyses of 142 cases of this series were evaluated and compared with the meningioma grades. Thereby, 25 cases disclosed, independent of the typical loss of one chromosome 22, cytogenetic features assumed to be progression-associated, e.g., the gain or loss of different chromosomes and the deletion of the short arm of one chromosome 1 (hyperdiploidy, increased hypodiploidy, 1p-), when correlated to the histological and morphometric findings or the high relapse rate. For meningioma diagnosis and grading, a practical guideline is proposed based upon histology, morphometry (Ki-67), and cytogenetics.

Monosomy 1p is correlated with enhanced in vivo glucose metabolism in meningiomas

The 2-[18F]fluoro-2-deoxy-D-glucose (FDG) uptake of 25 human meningiomas was preoperatively evaluated in vivo by positron-emission tomography (PET). After surgery, meningioma biopsies were analyzed cytogenetically. Five meningiomas showed partial monosomy for chromosome 1p additional to other typical chromosome aberrations. This aberrant karyotype was correlated with increased FDG uptake. Three of five meningiomas with monosomy 1p were classified as grade II according to WHO, while only one of 20 tumors without monosomy 1p was classified as grade II. Thus, monosomy 1p and elevated FDG uptake in PET are to be regarded as cytogenetic and metabolic parameters for the aggressiveness of meningiomas.

Chromosome abnormalities in meningeal neoplasms: do they correlate with histology?

Thirty-three meningeal neoplasms were karyotyped, and the results were compared with histologic features. Thirteen neoplasms had no discernible abnormality or sex chromosome loss only; nine had monosomy or structural abnormality involving only chromosome 22; and 11 had other chromosome abnormalities with or without chromosome 22 involvement. Histologic evidence of invasion was not associated with an abnormal karyotype in the three angioblastic tumors examined. All seven fibroblastic meningiomas had abnormal karyotypes, with monosomy 22 the most common change. Abnormal karyotypes were detected in 76% of syncytial and 55% of transitional meningiomas. When these results were combined with those from 259 meningeal tumors reported since 1987, abnormal karyotypes were detected in at least half of all histologic types. Chromosome changes secondary to those involving chromosome 22 may indicate additional areas of the genome that play a role in tumor progression. In the combined series, chromosome losses were most frequently observed in meningiomatous and transitional histologies; chromosomes 1, 6, 14, 18, and Y each were lost in 10 or more meningiomas, whereas only chromosome 20 was gained at the same frequency. Structural abnormalities most frequently involved chromosome 1. These changes are distinctly different from those observed in other common intracranial neoplasms, specifically astrocytic neoplasms.

Deletions on chromosome 22 in sporadic meningioma

Meningiomas are the second most common group of primary central nervous system tumors in humans. Cytogenetic and molecular studies imply that genes involved in the primary development of meningioma reside on chromosome 22. The recently characterized neurofibromatosis type 2 gene (NF2) has been shown to be mutated in two cases of sporadic meningioma, suggesting that this is the chromosome 22 gene which is involved in tumorigenesis. We have investigated a series of 170 meningiomas by deletion mapping analysis with 43 markers from chromosome 22 to ascertain if NF2 is the only gene on this autosome that is inactivated. Half of the tumors showed results consistent with monosomy for chromosome 22, whereas 13 cases showed terminal deletions of 22q, including the NF2 region. Homozygous (complete) deletions were detected in tumors from two patients. In one of them complete loss was found at the NF2 locus and cosmid contigs from the region were used to determine the extent of the deletions. The second tumor showed homozygous loss of two large genomic regions outside the NF2 region. These aberrations were confined to only one part of this large tumor, suggesting that they may be involved in the later stages of meningioma development. An additional four tumors had interstitial deletions on chromosome 22, in three of them without overlap with NF2. Our results show that NF2 is completely inactivated in sporadic meningioma but do not rule out the possibility that additional chromosome 22 loci are important in tumorigenesis.

Allelic loss at 1p is associated with tumor progression of meningiomas

Next to chromosome 22 anomalies, deletions of the short arm of chromosome 1 have previously been described as the most frequent alteration detected by cytogenetic analysis of meningiomas. To determine the incidence of these deletions, we have analyzed a series of 50 meningiomas for the loss of alleles at four chromosome 1 loci. Thirteen samples displayed LOH for the markers studied; in one instance, the results were compatible with loss of the entire chromosome 1, whereas in the other 12 samples deletions of the short arm were observed. Eleven of the meningiomas had previously been shown to have loss of alleles on chromosome 22, and 12 of them were characterized by increased tumor aggressiveness. These findings suggest that deletion of Ip (or the alteration of a locus located there) might represent a secondary, but nonrandom alteration in meningiomas, perhaps contributing to meningioma tumor progression.

Abnormalities of chromosome 22 in pediatric meningiomas

Cytogenetic studies of eight meningiomas in young children or adolescents were performed. Two tumors exhibited normal karyotypes. Two tumors from patients with bilateral acoustic neurofibromatosis demonstrated monosomy 22 as the only abnormality. Four patients had more complicated karyotypes in which one or both of the chromosomes 22 were missing or structurally altered. The most common secondary changes in these four tumors involved monosomy or structural abnormalities of chromosome 6. These findings confirm that the primary cytogenetic changes in meningioma are similar in children and adults. Molecular analyses of pediatric meningiomas with deletions or translocations of chromosome 22 will be useful for identifying the role of chromosome 22 tumor suppressor genes in this disease.

Case of meningioma with del(1)(p32) as sole anomaly

We studied a case of typical syncytial meningioma. Cytogenetic analysis of the tumor cells showed a karyotype with normal chromosomes 22 and only one anomaly, del(1)(p32). Cases of meningiomas with normal chromosomes 22 and other anomalies are rare, and it is difficult to correlate their histologic characteristics and biologic behavior.

Correlation between cytogenetic and histopathological findings in 75 human meningiomas

The correlations between cytogenetic and histopathological findings were analyzed in 75 human meningiomas. The tumors were classified according to increasing degrees of anaplasia into three grades: Grade I, benign; Grade II, atypical; Grade III, anaplastic. In 45 tumors of Grade I (benign), we more often observed a normal karyotype or monosomy 22. In 23 tumors of Grade II (atypical), we observed karyotypes with structural and/or numerical abnormalities with the presence of telomeric associations in 8 of them. These last tumors were fibroblastic. In seven Grade III tumors (anaplastic), we also observed complex abnormalities, and in one case, we observed telomeric associations. Our observations show that complex chromosome abnormalities and telomeric associations are observed in tumors that histologically display a certain degree of anaplasia. It is possible that the result of histopathological and cytogenetic correlations might represent a prognostic factor in meningiomas.

1;19 translocation in human meningioma

BACKGROUND

Loss of chromosome 22 represents the most common chromosome abnormality (70%) in meningiomas. The remainder (30%) have a normal karyotype. Not only are the structural changes rare, they also occur simultaneously with various chromosome losses.

METHODS

The authors identified and studied the meningiomas of two patients with standard tumor cell culture technique and chromosome preparation.

RESULTS

Twenty karyotypes from each meningioma had a 46 modal chromosome number with t(1;19) (q21;p13) in all cells.

CONCLUSIONS

The sole change of the (1;19) translocation in meningioma, without any other changes such as chromosome loss, as shown in this study, is unique and has never been reported before in the literature, to the knowledge of the authors. Additional study is needed to learn more about the rate of occurrence and the significant impact on meningeal tumor genesis.

Chromosome 22 heterozygosity is retained in most hyperdiploid and pseudodiploid meningiomas

Hyperdiploid or pseudodiploid modal chromosome numbers were found characterizing six human meningiomas, and all six tumors were disomic for chromosome 22. The scarce previous reports on the subject suggest that, in these cytogenetic subgroups of meningiomas, duplication of the retained chromosome 22 occurs after the loss of the other member of the pair, thus correlating well with the main characteristic of meningiomas, that is, losses of 22. To verify this question, molecular genetic analyses were performed on DNA pairs from blood and tumoral samples of all six cases, using polymorphic markers for chromosome 22. Restriction fragment length polymorphism studies failed to show any loss of heterozygosity for markers located on this chromosome in all six cases, suggesting that a different mechanism to that previously proposed might take place in the hyperdiploid or pseudodiploid meningiomas; perhaps a submicroscopic involvement (microdeletions or inactivating mutations) of the meningioma locus (both alleles) may result in an effect similar to that produced by monosomy 22 (which probably unmasks recessive mutations on the retained allele), enhancing the development of meningiomas.

Abnormalities of chromosome 22 in human brain tumors determined by combined cytogenetic and molecular genetic approaches

Southern blot hybridization studies were performed on a panel of 130 blood/tumor samples from brain neoplasms including all major histologic subtypes: 50 meningiomas, 18 neurinomas, 56 gliomas, and six others. To detect abnormalities involving chromosome 22, polymorphic probes were used to analyze eight loci located in this chromosome: D22S9, IGLV, D22S20, D22S32, MB, PDGF-B, D22S80, and D22S171. Loss of heterozygosity (LOH) was observed in 40 cases including monosomy, terminal, and interstitial deletions, which suggest the location of recessive tumor genes in certain chromosome 22 subregions (22q11.3-q12 in neurinomas and meningiomas, and 22q13 in malignant gliomas). Cytogenetic studies were performed in parallel on the same tumors, in most instances corroborating the presence of abnormalities for chromosome 22. Nevertheless, discrepancies between the cytogenetic and molecular findings were observed in several cases, suggesting that the use of both methodologies in combination might provide key information on the incidence and extent of the abnormalities involving chromosome 22 in human brain tumors.

Cytogenetic study of a pineocytoma

The cytogenetic findings based on G-banding in a pineocytoma detected in a 29-year-old woman are reported. The chromosomal study showed numerical alterations involving chromosomes X, 5, 8, 11, 14, and 22, structural alterations of chromosomes 1, 3, 12, and 22, as well as various markers. Tumors of the pineal region are infrequent, and this is the first report of a pineocytoma studied cytogenetically.

Abnormalities of chromosome 22 in meningiomas and confirmation of the origin of a dicentric 22 by in situ hybridization

We report three cases of meningioma. Case 1 had a dicentric chromosome number 22 resulting in partial monosomy for a portion of the q-arm, i.e., 46,XX,idic(22)(pter-->q11.2::q11.2-->pter) and 46,XX,psu dic(22)(pter-->q11.2::q11.2-->pter), which was the sole clonal abnormality. The origin of the dicentric chromosome from 22 was confirmed by in situ hybridization studies, using biotin-labeled alpha centromeric DNA probes for the acrocentric chromosomes. Case 2 had two distinct clonal abnormalities: deletion of 22q and monosomy of 22. Case 3 also had a deleted 22q.

Supernumerary ring chromosomes in five bone and soft tissue tumors of low or borderline malignancy

Five tumors (two myxoid malignant fibrous histiocytoma, two dermatofibrosarcoma protuberans, and one parosteal osteosarcoma) with ring chromosomes as the sole cytogenetic anomaly or as the only structural rearrangement were observed in a series of 60 karyotypically abnormal, nonlipogenic bone and soft tissue tumors (BST). All five tumors were of borderline or low malignancy. These findings support the suggestion that supernumerary ring chromosomes as the sole structural chromosomal aberration are not associated with any particular histopathologic diagnosis but may characterize a group of BST of borderline or low malignancy.

Cytogenetic findings in typical and atypical meningioma

Comparative pathological and karyotypic findings of a typical and an atypical meningioma in two different patients are presented. The chromosomal abnormalities observed appeared unique for the histopathological subtype of the tumor. Cytogenetic analysis of atypical meningioma has not previously been reported.

Parallel karyotypic evolution and tumor progression in uterine leiomyoma

Cytogenetic evidence of clonal evolution was detected in five uterine leiomyomas. In two tumors, two clones were found, the third tumor had four, the fourth had nine, and the fifth had 12 clones. The first tumor had trisomy 12 as the primary anomaly and a sideline that also contained a del(7)(q21q31). Both clones of the second tumor had three structural changes in common but differed by the presence in the more advanced clone of an inv(7)(q31q34). Two cytogenetically unrelated pairs of clones were seen in the third tumor. One clone had a stemline of 46 and an r(1); a sideline had developed through duplication of this clone. The other pair had a del(7)(q21q31) in common. The last two tumors both had t(12;14)(q14-15;q23-24) as the primary abnormality. They also had a high frequency of telomeric associations that involved certain chromosome arms only. One of the secondary changes in the fourth tumor was a del(7)(q21q31); the principal secondary change in the fifth case was a ring chromosome 1 of variable size in the different clones. The analysis of these five uterine leiomyomas and the collation of the results with previously obtained data lead us to conclude that del(7)(q21q31) is secondary to t(12;14) and + 12 in this tumor type, and that ring formation involving chromosome 1 material, often with duplication of segments, is a common phenomenon during clonal evolution. The fact that the tumors were classified as cellular and had an increased mitotic rate indicates a parallel development between histologically detectable tumor progression and cytogenetically recognizable clonal evolution in uterine leiomyomas.

Chromosome abnormalities in multiple meningiomas of a child

We report the cytogenetic findings in two meningiomas from a child presenting with multiple meningiomas. In contrast to the chromosomal profile of adult meningiomas, both tumors studied revealed excess of chromosomes in addition to monosomy 22. This difference is remarkable considering several reports indicating that childhood meningiomas behave differently and have a worse prognosis than those in adults.

Correlation between cytogenetic and histopathological findings in 65 human meningiomas

The correlations between cytogenetic and histopathological findings were analyzed in 65 cases of human meningiomas. Clonal chromosome abnormalities were present in 28 cases (43%). The overall female/male ratio was 1.7, but it was 1.1 in the group of 28 cases with chromosomal abnormalities. Abnormalities of chromosome 22 as sole abnormality predominate in the female patients. The mean age of patients with normal karyotype was significantly lower (50.7 years) than that of patients with chromosome changes (57.3 years). The tumor origin was predominantly at the base in the patients with normal karyotype but different at the convexity, falx cerebri, and spinal cord. The five abnormal cases from the spinal cord all showed involvement of chromosome 22. The proportion of chromosome anomalies was different in the various histological types, and a significant difference was found between the meningotheliomatous (23%) and psammomatous (58%) types. The cytogenetically abnormal cases of the psammomatous type all showed involvement of chromosome 22. In three patients with multiple meningiomas, we found different karyotypes in the different tumors of the same patient, which may indicate a multifocal origin of the tumors.

Incidence and origin of dicentric chromosomes in cultured meningiomas

Based on the cytogenetic findings in 32 human meningiomas, an analysis of dicentric chromosomes, usually present in cultures from meningiomas, has been performed. The incidence and origin of such markers have been analyzed and the chromosomal composition of the stem line in the corresponding sample established (i.e., normal karyotype, -22 as the sole chromosomal deviation, or complex karyotypes in addition to #22 abnormalities). More than 10 dicentric chromosomes were found in 12 of 32 meningiomas (37.5%). Sixty-eight of the markers could be identified individually or as belonging to a chromosome group. Fifty-three percent of the meningiomas characterized by a complex stem line karyotype also displayed dicentric chromosomes in variant cells, whereas only 12.5% of meningiomas with a normal diploid stem line showed such chromosomal aberrations. Chromosomes of groups C and D participated most frequently in the genesis of dicentrics; however, chromosomes 19, 20, 3, 6, and 13 were the most frequently involved. Thus, the existence of a nonrandom pattern of involvement supports the fact that dicentrics might play a biologic role in the progression of human meningiomas.