Proliferative potential of human meningiomas of the brain. A cell kinetics study with bromodeoxyuridine

Does Parenteral Nutrition Increase Tumor Growth? A Review

Total parenteral nutrition (TPN) is a supportive therapy commonly used in clinical oncology, in spite of its possible interference on tumor growth. In fact, studies performed on animals have demonstrated that TPN increases tumor growth and that load and quality of amino acids are probably the main factors involved. In contrast, some authors obtained a decrease in tumor growth using a special amino acids mixture or a TPN formula rich in lipids. However, data collected on animals are not transferable to humans owing to the large difference between tumor-host weight ratio and tumor doubling time. Analy sis of the studies on effect of TPN on tumor growth in humans has not demonstrated a bad effect, but the results reported in the literature are limited by the small number of patients, the lack of a sure and reproducible method to analyze tumor growth, and some methodologic defects. In conclusion, it is not evident that TPN is dangerous for cancer patients. However, it may be possible in the future to employ different formulas to improve the host nutritional status and inhibit tumor growth.

Ploidy and Proliferation Evaluated by Flow Cytometry. An Overview of Techniques and Impact in Oncology

Flow cytometric methods for the assessment of nuclear and chromosomal DNA content and of cell proliferation (including methods based on pulse-chase of bromodeoxyuridine and on monoclonal antibodies against nuclear oncoproteins and proliferation-associated antigens) are illustrated by examples and analyzed critically. The impact of most of these techniques for the study of human solid tumors, with exception of nuclear DNA content evaluation, appears still limited. In particular, new studies of cell lines and clinical material from human tumors using new proliferation markers and multiparameter flow cytometry are necessary to solve a considerable number of methodologic and scientific problems.

A canine case of skull base meningioma treated with hydroxyurea

An 11-year-old female miniature schnauzer was tentatively diagnosed with the skull base meningioma, based on several examinations. Because surgical treatment was difficult, and outpatient radiation therapy was not available in the local area, chemotherapy with hydroxyurea combined with dexamethasone was selected. The patient's clinical symptoms improved after one week of treatment, and the tumor size was obviously reduced on MRI performed 37 days after treatment began. The patient received hydroxyurea for 7 months, with symptoms remaining stable, and the tumor re-increased to almost the same size at 7 months as that at the initial examination. At that time, hydroxyurea was discontinued. The patient died from pulmonary edema 14 months after treatment began. Pathologically, the tumor was diagnosed as a meningioma.

Techniques to assess the proliferative potential of brain tumors

Assessment of brain tumor proliferative potential provides important prognostic information that supplements standard histopathologic grading. Many laboratories rely on mitotic figures to quantify the proliferative potential of brain tumors, but this conventional cellular proliferative index is subject to inter-observer variability and not consistently predictive for low-and high-grade tumors. Recent advancements in technology have made it possible to use proliferative indices as a standard supplement in pathology laboratories. Non-invasive tumor tissue measurements of cell proliferation can be performed using- bromodeoxyuridine labeling index (BrdU LI), flow cytometry (FCM), MIB-1 antibody to the Ki-67 antigen (MIB-1), proliferating cell nuclear antigen (PCNA), and argyrophilic nucleolar organizing regions (AgNOR). Each of these assays has been described in the literature with respect to its ability to predict tumor grade or outcome. At the present time MIB-1 and AgNOR are the simplest and most reliable of these techniques. In addition, advances in our understanding of the genetic alterations associated with proliferation promise to provide more specific markers of proliferative potential. Beyond the pathology laboratory, radiographic studies such as positron emission tomography (PET), single photon emission computed tomography (SPECT), and most recently magnetic resonance spectroscopy (MRS) have been used as follow-up measures, assessing response to treatment and tumor recurrence, rather than as predictors of response to treatment. These radiographic tools, however, have the potential to provide an assessment of tumor proliferation without the need for invasive measures. In this article, we present a review of the current techniques utilized to understand the proliferative potential of brain tumors.

Coexpression of hepatocyte growth factor/scatter factor (HGF/SF) and its receptor cMET predict recurrence of meningiomas

Hepatocyte growth factor/scatter factor (HGF/SF) and its receptor, the cMET tyrosine kinase participate in cancer invasion, angiogenesis and metastasis in a wide variety of neoplastic cells. Meningioma is a bening tumour, however, it has a high rate of recurrence after surgery; the most important factor to predict relapse is the extent of surgical resection, several other potentially predictive factors have been studied with poor results. We examined by immunohistochemistry the expression of HGF/SF and its cMET receptor in a group of patients with benign meningioma with or without recurrence (n = 17 and n = 25, respectively), after a minimal follow-up of least 6 years. Expression and coexpression of HGF/SF and cMET were compared with cell proliferation index, vascular density and clinical outcome. Coexpression of HGF/SF and cMET in meningiomas had a significant association with cell proliferation index and with recurrence (P < 0.037). Determination of HGF and cMET coexpression in meningiomas could be used as a predictor of recurrence.

Meningiomas: Updating Basic Science, Management, and Outcome

BACKGROUND

Meningiomas are biologically complex and clinically and surgically challenging. These features, combined with the rewarding potential for cure, make them of great interest to neurologists, neurosurgeons, and neuroscientists alike.

REVIEW SUMMARY

Initially, we review the clinical context of meningiomas, particularly recent changes in histopathological classification, diagnosis, and neuroimaging. Secondly, the underlying basic science as it has evolved over the last decades is summarized. The status of areas recently of intense interest, such as steroid hormone receptors and oncogenic viruses is described. Additionally, emerging areas of great promise, such as cytogenetics and molecular biology are presented. Lastly, we describe recent advances in management. In particular, skull-base surgery, image-guided surgery, and advances in radiotherapy are emphasized. The possible impact of basic research on management and outcome is also outlined.

CONCLUSIONS

Although usually benign and amenable to cure, meningiomas still present significant diagnostic and treatment challenges. Advances in basic science, surgery, and adjuvant therapy are widening the potential for safe, effective, evidence-based management leading to even better outcomes

Proliferation rate of intracranial meningiomas as defined by the monoclonal antibody MIB-1: correlation with peritumoural oedema and other clinicoradiological and histological characteristics

Paraffin-embedded surgical specimens from 55 meningiomas were immunostained after microwave processing using the streptavidin/peroxidase method and the monoclonal antibody (moAb) MIB-1 to the Ki-67 antigen. The authors assessed proliferative labelling index (LI) from a series of surgically removed meningiomas using immunohistochemical methods and MIB-1, and they correlated this index with clinical, radiological, and histological factors. No relationship was found between LI, sex, age, resection and histological grades, or volume. Symptoms, location, and peritumoural oedema did have a significant relationship to the MIB-1 LI. The symptomatic patients, i.e. those with tumours at the base of the skull and with GR3 peritumoural oedema (grade 3), had a greater chance of higher MIB-1 LI. It was proven that the increase of one unit in peritumoural oedema classification gave an increased risk of 3.312 and an LI greater than 3%. The authors also discuss the different methods of evaluating LIs in meningiomas, based on the available literature.

Prognostic significance of cyclin a expression in meningiomas

Unconstrained cell proliferation is characteristic of tumors. It is caused by the functional disorders of proteins that constitute the cell cycle mechanism. The cell cycle is controlled by cyclins, cyclin-dependent kinases, and cyclin-dependent kinase inhibitors. Many reports have proved, in cancers, that cyclins, cyclin-dependent kinases, and cyclin-dependent kinase inhibitors are out of control. Cyclin A is a protein that regulates critical transition of the cell cycle. The expression of cyclin A in meningiomas by immunohistochemical method was investigated. Furthermore, the correlation among cyclin A expression, clinical course, and proliferative potential were also evaluated. Seventy-seven meningiomas were studied. The mean cyclin A labeling indices were as follows: benign meningiomas, 1.01% +/- 0.62%; atypical meningiomas, 4.23% +/- 1.82%; and anaplastic meningiomas, 7.72% +/- 0.88%. Analyses of variance showed that significant differences existed between tumor grades for cyclin A labeling indices. A linear positive correlation between the cyclin A labeling index and bromodeoxyuridine labeling index was observed. The multivariate analysis using Cox's hazards model showed a high cyclin A labeling index (>3%) was a significant risk factor for recurrence. A high Ki-67 labeling index (>5%) and high tumor grade (World Health Organization grade II, III) were also significant risk factors for recurrence. These results suggested that the evaluation of cyclin A expression in meningiomas provides significant clinical information, especially as an independent prognostic indicator.

Research progress in the last quarter of the 20th century at the University of Tokyo and Tokyo Women's Medical University

Professor Keiji Sano described the history of neurosurgery in Japan until 1975. After World War II, not only neurosurgery but all fields of medicine were devastated in Japan. Professor Sano contributed greatly to the reform and modernization of neurosurgery during that very difficult era in Japan. He performed much research by himself and also as a leader of research groups on stereotactic and functional neurosurgery, cerebrovascular diseases, head injuries, and brain tumors. He organized the Fifth International Congress of Neurological Surgery in Tokyo in 1973. I succeeded in the chairmanship of the Department of Neurosurgery of the University of Tokyo in 1981. We have performed research on the treatment of brain tumors and cerebrovascular diseases. To obtain the best results for brain tumor treatment, we have introduced several new radiotherapeutic methods, such as the gamma knife, heavy-particle irradiation, and the photon radiosurgery system. To improve surgical treatment, we have energetically engaged in medical engineering research on computer-assisted surgical systems (intraoperative monitoring and navigation systems). We have also performed much research on chemotherapy and immunotherapy. In the field of cerebrovascular diseases, the main research projects have been focused on the mechanism and treatment of vasospasm and brain edema after subarachnoid hemorrhage. I summarize the results of our research performed in the Department of Neurosurgery of the University of Tokyo until 1992 and at Tokyo Women's Medical University after 1992, in the last quarter of the 20th century.

Stabilization of disease progression by hydroxyurea in patients with recurrent or unresectable meningioma

OBJECT

The management of certain meningiomas of the skull base and those involving the dural venous sinuses remains a challenge. In recent reports it has been suggested that hydroxyurea chemotherapy can cause regression of unresectable and recurrent meningiomas. The authors report their experience in using hydroxyurea for the treatment of patients with recurrent or unresectable meningiomas.

METHODS

Hydroxyurea was administered at a dosage of approximately 20 mg/kg/day to 11 women and nine men (median age 59 years, range 31-75 years) with recurrent or unresectable intracranial meningiomas (12 basal, two parasagittal, and six multiple). In 16 patients the meningiomas were benign, in three they had atypical features, and in one the meningioma was malignant. All patients had measurable residual disease. Four patients with benign meningiomas had previously received radiotherapy (two were treated with conventional fractionated radiotherapy and two with stereotactic radiosurgery), three with atypical meningiomas received conventional fractionated radiotherapy, and the one with a malignant meningioma received conventional radiotherapy with additional stereotactic radiosurgery. Tumor enlargement was documented in all patients on neuroimages obtained before initiation of hydroxyurea therapy. All patients were evaluable for response to therapy. In 12 patients with benign meningiomas, the disease had stabilized on neuroimages obtained posttreatment (median duration of treatment 122 weeks, range 8-151 weeks), and two of these showed clinical improvement. One patient with a benign meningioma experienced a minor partial response that was noted after 39 weeks of treatment and was confirmed on neuroimaging and clinical evaluations. In three others with benign meningiomas, progression was confirmed on neuroimages obtained after 41, 55, and 66 weeks, respectively: the 1-year freedom from progression rate was 0.93 (standard error 0.07) in patients with benign meningiomas. In three patients with atypical meningiomas, the tumors had progressed on neuroimages obtained after 12, 19, and 45 weeks, respectively. In the patient with a malignant meningioma, progression was confirmed on neuroimages obtained at 24 weeks. Hydroxyurea has been reasonably well tolerated, although one patient discontinued therapy because of moderate myelosuppression.

CONCLUSIONS

Although tumor regression appears uncommon, these results indicate that hydroxyurea may arrest progression of unresectable or recurrent benign meningiomas.

PCNA and Ki-67 in central nervous system tumors: correlation with the histological type and grade

Determination of proteins in the control of proliferation in normal cells helps a better understanding of cellular transformation and proliferation mechanisms. Measurement of proliferative activity is important in determining the tumor grade, recurrence span and malignancy. Proliferating cell nuclear antigen (PCNA) and Ki-67 are two of the nuclear markers used to demonstrate the proliferative phase of the cell cycle. In the present study, 63 central nervous system (CNS) tumors of various histologic types, diagnosed in Cukurova University Medical Faculty. Department of Pathology and graded according to WHO grading system were examined for PCNA and Ki-67 monoclonal antibodies using immunohistochemistry. Results were analyzed with statistical methods. Distribution of PCNA and Ki-67 LI (labeling index) values were determined for different tumor types. The highest PCNA and Ki-67 LI values were detected in medulloblastoma, malignant meningioma, primitive neuroectodermal tumor (PNET) and glioblastoma (GBM) groups, while pilocytic astrocytoma, meningioma, craniopharyngioma and oligodendroglioma showed the lowest values. In such tumors, the correlation between the increasing grade and PCNA and Ki-67 LI values were statistically significant. A correlation between the clinical outcome and Ki-67 and PCNA LI values was also detected. Conclusively, both markers can be used to evaluate the tumor grade and to asses the possibility of recurrence and malignancy in CNS tumors.

[Gross tumor volume (GTV) and clinical target volume (CTV) in radiotherapy of benign skull base tumors]

Skull base tumours represent about 35 to 40% of all intracranial tumours. There are now many reports in the literature confirming the fact that about 80 to 90% of such tumours are controlled with fractionated radiotherapy. Stereotactic and 3-dimensional treatment planning techniques increase local control and central nervous system tolerance. Definition of the gross tumor volume (GTV) is generally easy with currently available medical imaging systems and computers for 3-dimensional dosimetry. The definition of the clinical target volume (CTV) is more difficult to appreciate; it is defined from the CTV plus a margin, which depends on the histology and anterior therapeutic history of the tumour. It is important to take into account the visible tumour and its possible extension pathways (adjacent bone, holes at the base of skull) and/or an anatomic region (sella turcica + adjacent cavernous sinus). It is necessary to evaluate these volumes with CT Scan and MRI to appreciate tumor extension in a 3-dimentional approach, in order to reduce the risk of marginal recurrences. The aim of this paper is to discuss volume definition as a function of tumour site and tumour type to be irradiated.

Expression of the proliferating cell nuclear antigen and clinicopathological features in intracranial meningiomas

PC10, a monoclonal antibody (mAb) to proliferating cell nuclear antigen (PCNA) is known to show immunoreactivity in paraffin-embedded specimens. The authors present the relation between PCNA expression and clinicopathological features in 38 intracranial meningiomas. PCNA scores were obtained by immunohistochemical staining of the paraffin-embedded sections using a streptavidin-biotin immunoperoxidase method with PC10 mAb. Univariate analysis showed that high PC10 scores were associated with old age (> or = 50 years old), male, recurrent tumours, and meningothelial type. However, these high scores did not reach a statistical significance (P> 0.05). PC10 scores of the basal meningioma tended to be higher than that of the hemispheric meningioma (P< 0.05). The staining intensity of PCNA was also markedly increased in basal meningiomas. It is suggested that the proliferative potential is higher in basal meningiomas than in hemispheric meningiomas. Moreover, these results could reflect high recurrence and difficulty in management of the skull base meningiomas.

Prognostic significance of p53 and p21WAF1/CIP1 immunoreactivity and tumor micronecrosis for recurrence of meningiomas

Recurrence is an important factor for prognosis of meningioma patients, this also occurring with some lesions diagnosed histopathologically as benign. To analyze their relationships with clinicopathological factors, p53 and p21WAF1/CIP1 immunoreactivity, 80 meningiomas were classified into four groups with regard to the World Health Organization (WHO) histological classification and recurrence: 40 cases of Group I (typical type)-NR (no recurrence); five cases of Group I-R (recurrence); 20 cases of Group II (atypical or anaplastic type)-NR and 15 cases of Group II-R. Micronecrosis was detected in 25% of Group II-NR and 73.3% of Group II-R (P = 0.007, odds ratio (OR) = 8.25, 95% confidence interval (CI) = 1.79-38.01). Patients receiving radiation therapy had a lower risk of recurrence (P = 0.041, OR = 0.20, 95% CI = 0.05-0.85). Immunoreactivity for p53 protein was positive in 22% of Group I and 54% or Group II (P = 0.005), and in 80% of Group I-R and 15% of Group I-NR (P = 0.006, OR = 22.7, 95% CI = 2.15-239.4). p21WAF1/CIP1 protein was detected in 22% of Group I and 48% of Group II (P = 0.017), but with no link to recurrence. Multivariate analysis also showed p53 immunoreactivity in Group I (benign lesions) and micronecrosis in Group II (atypical/anaplastic meningiomas) to be strong prognostic factors for recurrence (P < 0.05). These results indicate that p53 immunoreactivity and micronecrosis can help predicting recurrence of meningiomas.

Radiosurgery for malignant meningioma: results in 22 patients

Object. The initial treatment of malignant meningiomas in the past has included surgical removal followed by fractionated external-beam radiotherapy. Radiosurgery has been added to the options for treatment of primary or recurrent tumors over the last 10 years. The authors report their results of using gamma knife radiosurgery (GKS) to treat 22 patients over an 8-year period.

Methods. Twenty-two patients who underwent GKS for malignant meningioma between December 1991 and May 1999 were evaluated. Three patients were treated with GKS as a boost to radiotherapy and 19 for recurrence following radiotherapy. Outcome factors including patient survival, freedom from progression, and complications were analyzed. In addition, in the recurrent group, variables such as patient age, sex, tumor location, target volume, margin dose, and maximum dose were also analyzed. Univariate and multivariate analyses were performed.

Overall 5-year survival and progression-free survival estimates were 40% and 26%, respectively. Age (p ≤ 0.003) and tumor volume (p ≤ 0.05) were significant predictors of time to progression and survival in both univariate and multivariate analyses. Five patients (23%) developed radiation necrosis. Significant relationships between complications and treatment variables or patient characteristics could not be established.

Conclusions. Tumor control following GKS is greater in patients with smaller-sized tumors (< 8 cm3) and in younger patients. Gamma knife radiosurgery can be performed to treat malignant meningioma with acceptable toxicity. The efficacy of GKS relative to other therapies for recurrent malignant meningioma as well as the value of GKS as a boost to radiotherapy will require further evaluation.

Metastatic atypical meningioma: case report and review of the literature

Extracranial metastasis of an intracranial meningioma is rare. We discuss the clinical, radiological and histopathological presentation of an elderly man with pulmonary metastases from a recurrent meningioma of atypical histology, and review the literature pertaining to this phenomenon.

Luteinizing hormone releasing hormone increases proliferation of meningioma cells in vitro

The fact that meningioma shows at least a 2:1 predilection for women over men is considered to be due to endocrinological and paracrine regulation of the development of this tumour. The presence of receptors for the luteinizing hormone releasing hormone (LHRH) in gynaecological cancer permits the use of LHRH agonistic or antagonistic analogues with a direct effect or by the gonado-pituitary axis suppression in the treatment of these tumours. Therefore, the effect of LHRH on meningioma cells is tested in this study. Meningioma cells from three female patients were cultured and LHRH (50 ng/ml) was added to the growth medium daily, for fourteen days. At the end of this period the cells were counted by means of a Coulter Counter. The stimulating effects of LHRH on the increase of the amount of cells in the meningioma monolayer culture were 146% (p < 0.01), 134% (p < 0.05) and 141% (p < 0.05) of the control, respectively, for the three patients.

Histopathologic features and MIB-1 labeling indices in recurrent and nonrecurrent meningiomas

BACKGROUND

Predicting the behavior of meningiomas based on histopathologic features alone has remained problematic.

DESIGN

This study retrospectively compared several histopathologic features and MIB-1 labeling indices (LIs) in recurrent meningiomas with those of nonrecurrent meningiomas. Six histopathologic features, including mitoses, necrosis, loss of architectural pattern, hypervascularity/hemosiderin deposition, prominent nucleoli, and nuclear pleomorphism, were compared between 32 recurrent and 27 nonrecurrent meningiomas using Fisher exact tests. MIB-1 LIs (% positive tumor cell nuclei) were compared using the Wilcoxon rank sum test.

RESULTS

The patients in the recurrent group included 26 women (mean age, 55 years), who developed 1 to 5 recurrences. Time intervals to the first recurrence ranged from 5 to 183 months (mean, 55 months). The nonrecurrent group included 21 women (mean age, 56 years), with follow-up ranging from 88 to 124 months (mean, 109 months). Of the histopathologic features evaluated, statistically significant differences between the recurrent and nonrecurrent groups were found only with respect to prominent nucleoli (P =.024) and nuclear pleomorphism (P <.001), both of which were more common in the recurrent group. In the recurrent group, 9 tumors were considered malignant (defined by brain invasion or metastasis) versus 2 of the nonrecurrent meningiomas. Nineteen percent of nonrecurrent tumors versus 41% of recurrent tumors had 2 or more of the 6 histopathologic features. MIB-1 LIs in the nonrecurrent group ranged from 0 to 8.3 (mean, 1.5) and were generally lower than those in the recurrent group (range, 0-32.5; mean, 5.4); no statistical difference was identified between these groups. No statistically significant difference with regard to histology or MIB-1 LIs was noted between the initially excised recurrent tumor and the most recently resected recurrence.

CONCLUSIONS

Of the histopathologic features examined, only prominent nucleoli and nuclear pleomorphism were found to be statistically more common in recurrent than nonrecurrent meningiomas. The mean MIB-1 LI was higher in the recurrent than in the nonrecurrent group, although there was no statistical difference between means and there was clear overlap with regard to MIB-1 LI ranges.

Correlation of the relationships of brain-tumor interfaces, magnetic resonance imaging, and angiographic findings to predict cleavage of meningiomas

OBJECT

The authors examined the relationships of brain-tumor interfaces, specific magnetic resonance (MR) imaging features, and angiographic findings in meningiomas to predict tumor cleavage and difficulty of resection.

METHODS

Magnetic resonance imaging studies, angiographic data, operative reports, clinical data, and histopathological findings were examined retrospectively in this series, which included 126 patients with intracranial meningiomas who underwent operations in which microsurgical techniques were used. The authors have identified three kinds of brain-tumor interfaces characterized by various difficulties in microsurgical dissection: smooth type, intermediate type, and invasive type. The signal intensity on T1-weighted MR images was very similar regardless of the type of brain-tumor interface (p > 0.1). However, on T2-weighted images the different interfaces seemed to correlate very precisely with the signal intensity and the amount of peritumoral edema (p < 0.01), allowing the prediction of microsurgical effort required during surgery. On angiographic studies, the pial-cortical arterial supply was seen to participate almost equally with the meningeal-dural arterial supply in vascularizing the tumor in 57.9% of patients. Meningiomas demonstrating hypervascularization on angiography, particularly those fed by the pial-cortical arteries, exhibited significantly more severe edema compared with those supplied only from meningeal arteries (p < 0.01). Indeed, a positive correlation was found between the vascular supply from pial-cortical arteries and the type of cleavage (p < 0.05).

CONCLUSIONS

In this analysis the authors proved that there is a strong correlation between the amount of peritumoral edema, hyperintensity of the tumor on T2-weighted images, cortical penetration, vascular supply from pial-cortical arteries, and cleavage of the meningioma. Therefore, the consequent difficulty of microsurgical dissection can be predicted preoperatively by analyzing MR imaging and angiographic studies.

Atypical and malignant meningiomas: an outcome report of seventeen cases

Limited data are available concerning the outcome of patients with atypical and malignant meningiomas. We therefore analyzed the outcome of seventeen patients with meningiomas (9 atypical; 8 malignant) at Thomas Jefferson University Hospital between 1973 and 1996. Strict adherence to the 1993 WHO criteria for the typing of CNS tumors was maintained. The median potential follow-up period for all patients was 87 months. The age at diagnosis ranged from 22 to 72 (mean 51.8 years). There were 5 males and 12 females. The mean tumor diameter was 4.45 cm. Of the 16 cases where the extent of surgical resection was known, 4 were partial and 12 were complete resections. Six patients (35%) had dural or cortical invasion by tumor. Fifteen patients received postoperative megavoltage photon irradiation (mean 61 Gy). One of these fifteen pts. received an additional 20 Gy with Au-198 implantation and 1 received post-radiation chemotherapy for recurrent disease. The overall survival rate for all patients at 5 and 10 years were 87% and 58% respectively. The 5- and 10-year survival rates for atypical meningiomas were 87% and 58%; for malignant meningiomas the survival rates were 60% and 60% respectively. Five patients (30%) have died. Three of these 5 patients initially received less than 54 Gy to the tumor bed and have died of recurrent disease. Local disease progression was documented in 11 patients (65%) after surgery and in 3 patients (18%) after radiation. There was an improvement in performance status in 3 (18%) patients with a decline and no change seen in 1 (6%) and 13 (77%) respectively after receiving radiation. There appeared to be no difference in survival in patients as a function of dural or cortical invasion. Long term survival is possible for patients with atypical and malignant meningiomas treated with surgery and post-operative radiation. We are unable to distinguish a difference in outcome between these two pathological entities. Dural and cortical invasion were not associated with a decrease in survival. In addition, improved tumor control and survival may be associated with increased radiation dose.

Prognostic significance of MIB-1, p53, and bcl-2 immunoreactivity in meningiomas

Sixty biopsy specimens of meningiomas, including 37 benign, 10 atypical, and 13 malignant meningiomas, were examined immunohistochemically using the monoclonal antibodies MIB-1 (a cell proliferation marker), p53, and bcl-2 (two apoptosis-associated markers). Benign meningiomas were subdivided into two groups: group 1, 29 tumors without recurrence; and group 2, eight tumors with recurrence after complete surgical resection. The mean MIB-1 labeling index (LI) values+/-SD were 1.3+/-3.2% for the benign, 9.3+/-6.9% for the atypical, and 15.0+/-16.9% for the anaplastic meningiomas. The mean MIB-1 LI+/-SD in group 1 tumors (n = 29) was 1.06+/-1.15%, and in group 2 tumors (n = 8), 2.3+/-4.76% (P = .028). p53 protein expression was found in 10.8% of the benign (10.34% of group 1 and 12.5% of group 2), 50% of the atypical, and 77% of the anaplastic meningiomas. bcl-2 protein expression was observed in 21.6% of the benign, 20% of the atypical, and 46.1% of the anaplastic meningiomas. Among the benign meningiomas, group 2 tumors expressed significantly more often bcl-2 protein (62.5%) than group 1 neoplasms (10.3%). Our results indicate that (1) in meningiomas, a good correlation exists between histological grading, MIB-1 and p53 protein expression, and (2) in benign meningiomas, the presence of bcl-2 protein expression together with high MIB-1 LI are associated with unfavorable prognosis of the disease.

S-phase fraction, 5-bromo-2'-deoxy-uridine labelling index, duration of S-phase, potential doubling time, and DNA index in benign and malignant brain tumors

Seventy-one histologically malignant brain tumors, 52 histologically benign brain tumors, and 14 cerebral metastases were characterized according to DNA content and proliferative capacity. DNA ploidy, DNA index (DI), S-phase fraction (SPF), 5-bromo-2'-deoxy-uridine (BrdUrd) labelling index (LI), duration of S-phase (Ts), and potential doubling time (Tpot) were assessed by flow cytometry (FCM). In histologically benign tumors, a high percentage of DNA diploid tumors and a low proliferative capacity in DNA diploid tumors were found. Histologically malignant tumors and cerebral metastases were both found to be characterized by a low percentage of DNA diploid tumors and a high proliferative capacity in DNA diploid tumors. The proliferative capacity of DNA aneuploid benign tumors and that of DNA aneuploid malignant tumors, however, appeared not to differ significantly. The number of DNA aneuploid tumors was small. Duration of S-phase was short (range 3.9-4.7 hr) and appeared not to differ between the three groups. From this, the observed differences in Tpot values should be accredited mainly to differences in LI. High-grade as well as low-grade gliomas both appeared to be characterized by malignant (FCM) features, i.e., 1) a high percentage DNA aneuploidy, 2) a high mean DI (for DI > 1), and 3) a high proliferative capacity.

High PCNA index in meningiomas resistant to radiation therapy

PURPOSE

Meningiomas are common intracranial tumors, often well controlled with surgical resection alone. While the efficacy of radiation therapy in improving local control and progression-free survival is well documented, prognostic data substantiate factors that are predictive of poor local control following definitive radiation therapy. PCNA is a DNA polymerase expressed at the highest levels in the S-phase, the most resistant portion of the cell cycle to ionizing radiation in vitro. We investigated the possible correlation between the levels of PCNA expression and the clinical outcome of patients treated with definitive radiation therapy.

METHODS AND MATERIALS

Archival tissue was collected from 33 cases of meningioma treated at our institution for definitive radiation therapy between 1970 and 1990. Age-matched normal meningeal tissue and asymptomatic meningiomas removed at autopsy served as tissue controls. A standard ABC immumoperoxidase technique employing antibodies to PCNA, PC-10 (Dako, California) was used to stain specimen slides for PCNA. PCNA index was defined as the number of positive nuclei per 10 high-power fields at 400x magnification. Two independent observers scored the slides without prior knowledge of the cases at hand.

RESULTS

Patients with high PCNA index were less likely to be controlled by therapeutic radiation (p < 0.001, Kaplan-Meier). All patients with a PCNA index greater that 25 failed radiation therapy. Using multivariate analyses, malignant (but not atypical), histology and PCNA index were significant predictors of progression following radiation therapy (p < 0.05, log rank).

CONCLUSION

PCNA index may be a useful adjunct to more standard histopathologic criteria in the determination of meningioma local control and progression-free survival following therapeutic irradiation. Data on a more expanded population evaluated on a prospective basis will be needed before such criteria are routinely employed in the clinical setting.

Immunohistochemical examination of proliferative potentials and the expression of cell cycle-related proteins of intracranial chordomas

The difference in biological features between recurrent and nonrecurrent intracranial chordomas has not been studied. In this study, proliferative potentials of chordomas were studied with an immunohistochemical staining method, mainly using anti-Ki-67 antibody, MIB-1, which is known to be available for archival paraffin sections, together with immunohistochemical studies on the expression of cell cycle or apoptosis-related proteins, including p53, cyclin D1, and bcl-2 proteins. The correlation among MIB-1 staining indices, the immunoreactivities of these proteins, and clinical courses of intracranial chordomas were analyzed retrospectively, and the statistically significant correlation between MIB-1 staining index (SI) and recurrence has been clarified. The mean MIB-1 SI of recurrent tumors was 10.2%, being shown to be higher than that of nonrecurrent tumors (2.8%). The immunohistochemically positive staining of cell cycle-related protein, especially p53 and cyclin D1 proteins, correlated well with recurrence and high MIB-1 SI. In conclusion, both the examination of proliferative potentials of chordomas using MIB-1 SI and the study of the immunoreactivity of p53 and cyclin D1 proteins are important for their biological and histopathological analyses and the prediction of future recurrence.

Progesterone and estrogen receptors in meningiomas: prognostic considerations

Meningiomas often contain steroid hormone receptors, but the correlation of receptor presence with patient outcome or mitotic index is unclear. Intracranial meningiomas from 70 patients (27 males and 43 females, mean age 52.9 + 1.7 years [mean +/- standard error of the mean], range 15-78 years) were evaluated immunocytochemically for female sex hormone receptors using specific monoclonal antibodies. Prognostic correlations were determined using statistical analyses that included clinical and histological variables. Twenty-eight tumors were benign, 27 had atypical features, and 15 were malignant. Thirty tumors were meningotheliomatous, 11 were fibroblastic, 28 were transitional, and one was secretory. Twenty-nine of the 70 primary tumors recurred (mean interval to recurrence 50.1 +/- 10 months). The mean progression-free follow-up period for patients without recurrence was 82.1 +/- 7.7 months. Nuclear staining for the progesterone receptor (PR) was found in 58 cases (83%) and PR status was scored as 0 (0% nuclei positive), 1 (< 1%), 2 (1-9%), 3 (10-49%), or 4 (> 50%). Only six tumors (8.6%) contained nuclear estrogen receptor (ER) staining, which was limited to a small number of nuclei (< 1%). Fisher's exact test (two-tailed) showed an inverse correlation between tumor grade and PR staining score (p < or = 0.001), with 96% of benign and 40% of malignant meningiomas containing PR-positive nuclei. No correlation between age or histological subtype and PR score was detected. Meningiomas from female patients had more PRs (p < or = 0.05). Analysis of variance revealed that the mitotic index (total counts of mitoses per 10 high-power fields) for tumors with 0 PR staining (18 +/- 4.4) was higher (p < or = 0.0001) than for those with PR scores of 1 to 4 (4.3 +/- 1.9, 5.1 +/- 2, 2.2 +/- 0.8, and 1.7 +/- 0.9, respectively). Univariate analysis indicated that the absence of PR, high mitotic index, and higher tumor grade were significant factors for shorter disease-free intervals. Multivariate analysis showed that a three-factor interaction model, with a PR score of 0, mitotic index greater than 6, and malignant tumor grade, was a highly significant predictor (p < or = 0.0001) for worse outcome in patients harboring meningiomas. These data indicate that the presence of PRs, even in a small number of tumor cells, is a favorable prognostic factor for meningiomas.

Regrowth resistance as a likely significant contributor to treatment failure in drug-sensitive neoplastic diseases

Attempts to improve the effectiveness of therapy for neoplastic diseases have largely focused on increasing the cytotoxic efficacy of therapy. While this approach is logical, there is another approach, based on the concept of regrowth resistance, which offers an alternate means of improving treatment outcome. The term "regrowth resistance" refers to the reduction in treatment efficacy resulting from the regrowth of neoplastic cells between courses of therapy or even between doses of radiation therapy. Regrowth resistance is likely to play a significant role in determining the outcome of treatment in rapidly proliferating neoplasms. A reduction in the rate of tumor regrowth would increase the net effectiveness of cytotoxic therapy and would also inhibit the development of resistance to cytotoxic therapies.

MIB-1 staining index and peritumoral brain edema of meningiomas

BACKGROUND

Growth rates and tumor aggressiveness of meningiomas are thought to be closely related to brain edema development. However, histopathologic data alone are not consistently accurate predictors of the behavior and clinical course of a meningioma.

METHODS

The authors examined 57 histologically proven intracranial meningiomas to identify factors, including growth fractions determined by MIB-1 immunostaining, that may influence the development of meningioma-associated peritumoral brain edema. There were 54 benign, 2 atypical, and 1 anaplastic meningiomas. The MIB-1 staining index (SI) percentage was defined as the number of MIB-1 positive cells divided by the total number of tumor cells in a 1.037-square millimeter area on the slide. The extent of peritumoral brain edema was determined using preoperative magnetic resonance imaging. The extent of edema was classified as Grade 0,1, or 2 (GR0, GR1, or GR2), in order of increasing severity.

RESULTS

The MIB-1 SIs of the 57 cases ranged from 0.06-6.8% (median, 0.80%). There were 26 GR0, 20 GR1, and 11 GR2 edema cases. The MIB-1 SI rose in order of increasing edema severity. There was a statistically significant correlation between the MIB-1 SI and the extent of brain edema (P<0.0001), and also between the tumor size and the extent of brain edema (P=0.001). Meningothelial and atypical/anaplastic meningiomas were associated with peritumoral brain edema more often than any other subtype (P<0.005).

CONCLUSIONS

Growth fractions, as determined by MIB-1 immunostaining, rise with increasing severity of peritumoral brain edema, indicating a close relationship between tumor aggressiveness and edema development.

Colorectal cell kinetics

The assessment of cell proliferation in colorectal tissue may provide information with both prognostic and therapeutic implications. A variety of methods are available, including flow cytometric estimations of S phase fraction, immunohistochemical and autoradiographic visualization of exogenous and endogenous proliferation proteins, and morphological and stathmokinetic techniques. There is some correlation between Dukes stage and proliferation state features, and there is increased proliferative activity throughout the adenoma-carcinoma sequence. Data on cell proliferation rates are difficult to obtain. When correctly applied, the metaphase arrest technique remains the 'gold standard' of measuring proliferation, but its usefulness in clinical practice is limited. Recent studies have employed dual measurement flow cytometry and double labelling techniques to produce rate data.

Adjuvant combined modality therapy for malignant meningiomas

Malignant meningiomas constitute 10% to 15% of all meningiomas and limited information exists regarding adjuvant treatment of these aggressive primary brain tumors. Fourteen patients (eight men, six women), ranging in age from 28 to 61 years (median 51 years), were prospectively treated for primary malignant meningiomas according to an institutional protocol. All patients underwent surgery (gross-total in four and subtotal resection in 10 patients) followed in 2 to 4 weeks by involved-field radiotherapy (range 59-60 Gy, median dose 60 Gy). Two to 4 weeks after radiotherapy all patients were treated with adjuvant chemotherapy that included cyclophosphamide, adriamycin, and vincristine (CAV). Patients who underwent gross-total resection received three cycles, whereas those with subtotal resection received six cycles of CAV. Four patients required CAV dose reduction due to myelosuppression, and in three patients, myelosuppression prevented administration of the planned course of CAV. Four patients required transfusions (four received red blood cells, three received platelets), and two developed neutropenic fever without bacteriological documentation. Neuroradiographic response included three partial responses and 11 with stable disease. The median time to tumor progression was 4.6 years (range 2.2-7.1 years) and median survival was 5.3 years (range 2.6-7.6 years). The author concludes that combined modality therapy for the treatment of malignant meningiomas is associated with acceptable toxicity and a modest improvement in survival when compared to patients treated with surgery alone.

Comparison of MIB-1 (Ki-67) antigen and bromodeoxyuridine proliferation indices in meningiomas

Meningiomas from 40 adult patients were labeled immunohistochemically with monoclonal antibodies to bromodeoxyuridine (BUdR) and the Ki-67 antigen, MIB-1. The meningiomas were classified as classical, or benign (n = 31); atypical (n = 4); or malignant (n = 5). Meningeal sarcomas and hemangiopericytomas were excluded. The patient population consisted of 26 women and 14 men, ranging in age from 26 to 75 years. BUdR proliferation indices ranged from 0% to 5.8%, measurements that were expectedly lower than those for MIB-1, which ranged from 1.5% to 19.3%. MIB-1 proliferation indices were not significantly affected regarding steroid pretreatment or age. These results show a good correlation between the BUdR and MIB-1 proliferation markers (rs = 0.72; P < .0001), which supports the use of anti-MIB-1 as an alternative labeling tool to BUdR for the determination of the proliferation index in meningiomas, thus avoiding the administration of a potentially mutagenic drug.

Significance of proliferating cell nuclear antigen in predicting recurrence of intracranial meningioma

It is well known that the histological appearance of meningiomas often fails to predict accurately the clinical behavior of the tumor. Therefore, attention has turned from tumor histology to tumor biology. Proliferating cell nuclear antigen (PCNA), a cell cycle-regulated protein, has been recently characterized as the cofactor of DNA polymerase-delta, an enzyme required for DNA replication. The rate of synthesis of PCNA directly correlates with the proliferative state of cells. Immunohistochemical labeling of this antigen is now possible with monoclonal antibodies that allow for its demonstration in routinely fixed, paraffin-embedded specimens. In this study, the PCNA labeling index (LI) was determined for 83 meningiomas, including tumors with both benign and malignant clinical courses and with benign, atypical, and malignant histologies, apparent after total or subtotal resections. No statistical difference was found between the LI on recurrence and that found at initial presentation. In addition, stepwise multivariate regression analysis failed to identify any combination of factors (age, gender, race, age of specimen, tumor histology, Simpson grade of resection) that contributes to the predictive strength of the PCNA LI for tumor recurrence. However, for LIs less than 2%, only one of 26 gross totally resected tumors recurred (mean follow up 53 months); for LIs more than 7%, five of 13 gross totally resected tumors recurred (mean follow up 55 months). The difference in recurrence rates between gross totally resected meningiomas with PCNA LIs less than 2% and those with PCNA LIs more than 7% achieved statistical significance with a Fisher's exact probability equaling 0.011. The authors conclude that quantitative PCNA labeling of meningiomas is a promising technique that can provide meaningful prognostic information.

Intracranial meningioma masquerading as a primary pleuropulmonary tumor

Extracranial metastasis was found in an intracranial meningioma with low proliferative potential before the detection of the primary tumor. Pleuropulmonary tumors were incidentally detected on chest X-ray in an asymptomatic 25 year old female. Excised tumors of the right pleura and lung showed histological features similar to meningotheliomatous meningioma, which led to the discovery and excision of the intracranial tumor. Both tumors showed the same histologic pattern: meningotheliomatous meningioma with low mitotic activity. The proliferative component, determined by the monoclonal antibody Ki-67, was further evaluated in the primary tumor and the metastases of the present case, as well as in 12 other intracranial meningiomas. Ki-67 positive ratios at the primary and metastatic sites of the present cases were 1.2 and 1.1%, respectively, which is as low as other benign meningiomas, and this suggests that factors other than the proliferative potential is responsible for extracranial metastasis of meningioma.

Proliferative potential of meningiomas evaluated by proliferating cell nuclear antigen expression

Meningiomas are principally benign in nature. Some meningiomas, however, grow fast or recur even after total removal. The biological behavior of meningiomas often can not be predicted from conventional histopathological studies. A monoclonal antibody against proliferating cell nuclear antigen (PCNA) was used to investigate the usefulness of the PCNA index as a parameter to estimate the proliferative activity of meningiomas. Fifty-two meningiomas were examined. The mean PCNA index of recurrent meningiomas (3.37 +/- 0.92%) was significantly higher than that of non-recurrent meningiomas (1.12 +/- 0.51%) (p < 0.005). The PCNA indices of recurrent cases were all higher than 2.0%. A semilog linear regression analysis between tumor doubling time and PCNA index showed a significant correlation (r = 0.90, p < 0.05). An inverse linear correlation between PCNA index and interval to recurrence was observed (r = 0.62, p < 0.05). A good linear correlation was also shown between PCNA index and BUdR labeling index (r = 0.88, p < 0.01). The results of this study suggest that, providing the methods of tissue processing, immunostaining and counting of positive nuclei are unified, the PCNA index is a useful parameter for estimating the biological behavior of meningiomas.

Aggressive meningeal tumors: review of a series

A series of 25 patients with aggressive meningeal tumors was studied to determine the efficacy of various management options. The median age of the patients was 52 years, with a range of 13 to 73 years. A marked male preponderance (64%) was noted. Twenty of 25 patients experienced recurrence during a median follow-up time of 47 months. Survival and freedom from recurrence varied with histological diagnosis. Recurrence was noted sooner in patients who had received partial resections on first presentation of tumor than in those who had received total resections at first presentation. Survival time was also shorter for patients who underwent partial resections at first presentation than for patients who underwent total resections. Patients' prognoses did not improve as a result of either chemotherapy or radiotherapy. Of six patients with extracranial metastases, the median time to metastasis was 102 months, with a 5-year metastasis-free rate of 85%. The most common sites of metastasis in these six patients were lung and bone. In each tumor type, histological features used in diagnosis and radiological features studied from computerized tomography and magnetic resonance imaging were evaluated, compared, and discussed. Of eight patients studied with an in vivo bromodeoxyuridine (BUdR) labeling index (LI), seven showed an LI of 1% or more. The authors support the incorporation of the BUdR LI into the diagnostic process to provide a better estimate of the potential for tumor recurrence.

MIB1 staining index and scoring of histologic features in meningioma. Indicators for the prediction of biologic potential and postoperative management

BACKGROUND

The biology of brain tumors, including cell kinetics, has been studied. Recently, monoclonal antibody to Ki67 (MIB1), a nuclear protein related to cell proliferation, has been analyzed immunohistochemically using tissue prepared from paraffin embedded sections.

METHODS

The authors assessed the prognostic usefulness of various histologic indicators of the biologic potential of meningiomas in patients who underwent total resection (Simpson's Grade I and II) by evaluating the time to recurrence as an end point. Forty-three patients with a total of 36 meningiomas and 7 hemangiopericytomas were investigated by immunohistochemical analysis using MIB1.

RESULTS

MIB1 staining index (SI) and histologic score were well correlated with the recurrence-free interval (r = -0.6749, P = 0.002 and r = -0.4939, P = 0.027, respectively) and with each other (r = 0.7909, P < 0.001). The MIB1 SI and histologic score in the nonrecurrence group were significantly lower than those in the recurrence/metastasis group (P < 0.001 and P = 0.001, respectively). The values of these indicators showed that as the value increased, so did the recurrence rate.

CONCLUSIONS

Evaluation using the MIB1 SI and total histologic score of meningioma is useful in assessing the prognosis as well as postoperative management of these patients.

The prognostic implications of histologic classification and bromodeoxyuridine labeling index of mixed gliomas

To clarify the biological and clinical behavior and prognosis of mixed gliomas, 47 patients underwent intraoperative bromodeoxyuridine (BrdU) labeling studies. The mean age was 27.8 years at symptom onset and 31.8 years at labeling (median, 36 years). Forty-five tumors were supratentorial, 30 were frontal, and two were cerebellar; 16 were recurrent at labeling. The median labeling index (LI) was 1% (range, < 1 to 15.1%). Forty-six tumors has oligodendroglial and astrocytic elements, and one had astrocytic and ependymal elements. The median LI was 4.4% in recurrent tumors and < 1% in primary tumors. A higher BrdU LI correlated with an increased risk of recurrence and a shorter time to recurrence. During a median follow-up of 16 months, four patients died; each had a BrdU LI > or = 4.4%. The median time to recurrence was 4.5 months for tumors with BrdU LI's > 5% but was not reached for tumors with LI's < 5% (p < 0.003). The histologic grade of the oligodendroglial component correlated with the median time to recurrence (8 months for Smith Grade C tumors, not reached for Smith Grade B tumors; p < 0.05); there were too few cases to evaluate the median times to recurrence of Smith Grade A and Grade D tumors. The median time to recurrence was not reached for any astrocytic grade, and there were no significant differences in the Kaplan-Meier survival curves. These findings suggest that the BrdU LI and the grade of the oligodendroglial component of mixed gliomas have prognostic significance.

The significance of nucleolar organizer region (AgNOR) score in predicting meningioma recurrence

BACKGROUND

Argyrophilic nucleolar organizer region (AgNOR) has been demonstrated in recent studies of human brain tumors, including meningiomas. The authors used this technique in meningiomas to analyze whether the mean numbers of AgNOR per nucleus (AgNOR score) are related to the recurrence rate or the proliferative potential of meningiomas.

METHODS

AgNOR staining technique was applied to paraffin-embedded sections of 60 meningiomas. Twenty of these specimens also were investigated immunohistochemically with monoclonal antibody (MoAb) against DNA polymerase alpha (Pol.alpha) and with MoAb Ki-67 to compare the AgNOR score with the proliferative potential.

RESULTS

There was a statistically significant difference between the AgNOR score in nonrecurrent meningiomas (2.48 +/- 0.73) and recurrent histologically benign meningiomas after gross total resection (3.20 +/- 0.96) (P < 0.02). The recurrence rate of tumors after gross total resection with an AgNOR score of 3.0 or more was significantly higher than that with an AgNOR score of less than 3.0. The AgNOR score did not always correlate with Pol.alpha or Ki-67 score; the AgNOR score of malignant meningioma that had high proliferative score was not always high.

CONCLUSIONS

This study indicates that AgNOR staining appears to be a simple and useful method for estimating the probability of histologically benign meningioma recurrence even after gross total resection.

The application of 5-bromodeoxyuridine in the management of CNS tumors

A variety of clinical reports have described the application of the bromodeoxyuridine labeling index as an adjunct to conventional pathological examination of CNS tumors. This index has proven useful in predicting the clinical outcome associated with many such tumors. Furthermore, because of its efficacy as a radiosensitizing agent, bromodeoxyuridine (and the closely related iododeoxyuridine) has been used in combination with radiation therapy for malignant glial neoplasms, with some encouraging results. Although most studies suggest that bromodeoxyuridine is safe, there is evidence that this compound does have potential side-effects, including the observation that it is a mutagen and carcinogen in some experimental systems. A number of new alternative approaches for predicting the clinical outcome of CNS tumors has been developed based on an increased understanding of their molecular biology. However, until such approaches are better characterized, the clinical application of bromodeoxyuridine will continue to play an important role in predicting the clinical behavior of many CNS tumors.

The biology and pathology of selected skull base tumors

This paper describes the pathobiology of some of the more common skull base tumors. In addition to clinicopathologic features, emphasis is placed upon methods of diagnosis utilizing immunoperoxidase stains and molecular markers that may or may not impact upon prognosis.

Ki-67 immunoreactivity in human central nervous system tumors: a study with MIB 1 monoclonal antibody on archival material

Paraffin-embedded surgical specimens from 136 primary human central nervous system (CNS) tumors, including 50 meningiomas, 24 astrocytomas, 26 anaplastic astrocytomas, 9 glioblastomas, 8 oligodendrogliomas, 4 ependymomas, 1 anaplastic ependymoma, 2 subependymomas, 9 medulloblastomas, and 3 paragangliomas, were immunostained, following microwave processing, using a streptavidin/peroxidase method and the MIB 1 monoclonal antibody (mAb) against the Ki-67 antigen. The following mean Ki-67 labeling index (LI) values +/- SD were found: meningiomas, 2.47 +/- 1.83; astrocytomas, 2.03 +/- 2.03; anaplastic astrocytomas, 12.80 +/- 6.29; glioblastomas, 14.57 +/- 6.77; oligodendrogliomas, 5.06 +/- 4.78; ependymomas, 2.63 +/- 2.58; anaplastic ependymoma, 6.89; subependymomas, 1.79 +/- 1.54; medulloblastomas, 18.77 +/- 9.65; and paragangliomas, 2.19 +/- 2.51. Our findings indicate that while malignant CNS tumors always exhibited high Ki-67 LI values, and benign CNS tumors generally displayed lower values, increased immunoreactivity for Ki-67 epitopes (Ki-67 LI higher than 4) was noted in a number of meningiomas, astrocytomas, ependymomas, oligodendrogliomas and paragangliomas, contrasting with their benign histological features. Further investigations of the Ki-67 immunoreactivity in CNS tumors and systematic correlation with the postoperative follow-up of patients are necessary to determine the value of Ki-67 LI in predicting the biological behavior of CNS neoplasms.