a small percentage of intracranial meningiomas appear to have a malignant potential [ 13 ] . these rare histological subtypes characterized as malignant ( grade iii ) and atypical ( grade ii ) exhibit aggressive clinical behavior and are less studied than the classic benign ( grade i ) tumors [ 2 , 4 ] . objective of this study was to evaluate the incidence of atypical and malignant meningiomas and estimate their effect on recurrence , morbidity , and mortality . the postoperative behavior of the meningioma was followed and an effort was made to assess whether tumor 's location , histopathological subtype , and the extent of surgical resection were predictive factors for recurrence . from 1992 to 2007 , thirty - two patients with grade ii or iii meningioma , were treated surgically by the staff of the neurosurgical department of thessaloniki  g. papanikolaou  hospital . this study is a part of an observational retrospective study that comprised 353 patients with intracranial meningiomas who were operated at our department that period . hospitalization files , medical charts , and neuroradiological images obtained for the patients with meningioma , were analyzed with respect to clinical , operative , and laboratory pathological data . postoperative follow - up examinations , carried out by the department 's neurosurgeons were also used for this study .   the endpoint for recurrence was given by a computerized tomography scan ( ct ) or magnetic resonance image ( mri ) , showing a meningioma at a location contiguous with the previous surgery . the patients were brought in for follow - up examinations and neuroimaging controls at 3 and 6 months after surgery and then every year . they were evaluated via clinical examination or when that was not possible , by telephone interview . living patients interviewed by telephone described their symptoms referable to brain tumor . for deceased , relatives supplied information and reported if death had occurred due to the tumor or by unrelated causes . the karnofsky scale was used to evaluate the patients ' outcome after the operation . tumors were divided into types based on world health organization criteria , with grade i subtypes characterized as meningothelial , fibrous , psammomatous , transitional , stroviloid , epithelioid , angiomatous microcytic , secretory , chordoid . grade ii meningiomas are mentioned as atypical and grade iii as malignant .   for evaluating resection , this scale divides the extent of resection into 5 grades : grade i : complete removal;grade ii : complete removal with coagulation of dural attachment ; grade iii : complete removal , without coagulation of dural attachment or resection of involved sinus or hyperostotic bone;grade iv : subtotal resection;grade v : decompression biopsy . grade i : complete removal ; grade ii : complete removal with coagulation of dural attachment ;   grade iii : complete removal , without coagulation of dural attachment or resection of involved sinus or hyperostotic bone ; grade iv : subtotal resection ; grade v : decompression biopsy .   for patients with resection grades iv and v , endpoint for recurrence was enlargement of the remaining tumor , shown on mri or ct . the spss system ( version 15.0.1 ) was used for statistical analysis of the experiment 's results data . meningiomas of histological grading ii and iii accounted for 8.8% of all tumors in our series ( table 1 ) . the average patient 's age was 49  5 years at the time of surgery and the mean follow - up time was 4.3 years . follow - up control for patients with nonbenign meningiomas revealed that grade iii meningiomas recurred at a rate of 75% and grade ii meningiomas at a rate of 41.6% ( table 1 ) . survival rates for three , five , and ten years for these subtypes were much lower than the rest of the meningioma patients ( table 2 ) . three - year survival rate was 66.6% for atypical meningiomas , 33.3% for malignant meningiomas , and 86.3% for patients with grade five - year survival rate was 58.3% for atypical and 8.3% for malignant meningiomas , while for benign cases it raised to 74.3% . finally , ten - year survival rate was 33.3% for atypical and 0% for malignant meningiomas . on the contrary , six patients with malignant meningioma and two with atypical meningioma experienced tumor - related death . patients with grade ii resection ( complete resection with coagulation of the dura ) presented recurrence at 49% and grade iii ( complete resection of tumor , without coagulation of the dura or removal of affected sinus or bone ) patients recurred at a percentage of 67% , while 100% of grade iv and v patients developed tumor enlargement . the extent of surgical tumor removal was significantly associated with recurrence ( p < 0.001 ) . atypical and malignant meningiomas appeared to be more complex in resection than grade i tumors . v in the simpson scale , while the rate of nontotal tumor resection for the rest was 23.8% . more commonly , parasagittal ( 25% ) , convexity ( 18% ) , and tentorium ( 15% ) tumors appeared in our series . metastases appeared at the parotid gland , the thoracic spinal cord , and a different site of the brain . the majority ( 72% ) of recurrences were observed within two years from surgery and 96% within five years from surgery . according to some studies , malignant meningiomas comprise between 4.7 and 7.2% of meningiomas , whereas atypical meningiomas account for 1.0 to 2.8% [ 1 , 3 , 4 ] . the most known factor associated with their appearance is cranial irradiation [ 1 , 68 ] . though meningiomas are considered to be benign tumors , recurrence is observed frequently , with rates that vary between series [ 4 , 8 , 9 ] . the best accepted factor for prediction of recurrence is the 1957 simpson grading system for completeness of resection , which evaluated invasion of the venous sinuses , tumor nodules in adjacent dura , and infiltration of unresected bone by meningothelial cells as chief causes for recurrence . the recurrence rates that simpson refers to were 9% for grade i , 16% for grade ii , 29% for grade iii , 39% for grade iv , and 100% for grade v , respectively . these are peritumoral brain edema [ 2 , 10 ] , increase of neovascularization , cellular pleomorphism , nuclear atypia , the presence of macronuclei , atypical mitoses , necrosis , and brain invasion [ 8 , 12 ] .   in our series , recurrence was observed at a rate of 41.6% for grade ii tumors . for grade iii meningiomas , recurrence rate was 75% . besides the histological  aggressive  features we also found that recurrence was significantly associated with resection extent , according to simpson grading system . tumor location was not significantly related with meningioma reappearance , with the exception of certain locations whereas total resection was impossible . the rate of recurrence diminishes with time from operation . within 5 years from surgery , 96% of tumor reappearances three patients ( 37.5% ) of the patients with malignant meningiomas developed a metastasis ( parotid gland , thoracic spinal cord , and a different site of the brain ) . this shows that there is a high tendency of these tumors to develop metastases . the role of radiotherapy is well established in the treatment of atypical and malignant meningiomas [ 1 , 1316 ] . patients with these types of tumor are sent for radiotherapy postoperatively , if total resection is not possible . this is more frequent at tumor locations with difficult or high - risk access , where the surgeon tends to be less aggressive . conventional external beam radiation is being used for years and stereotactic radiosurgery is reported for unresectable tumors [ 3 , 17 ] . in addition to that , lower recurrence rates were observed in patients undergoing immediate postoperative radiation . another study supports that any tumor remnant radiologically demonstrated on postoperative imaging should be treated with radiosurgery and that postoperative radiotherapy after a first - time resection should be reserved for tumor remnants too large for radiosurgery and for which a second - stage operation is not planned . in our study , five patients with grades ii and iii meningiomas were sent for stereotactic radiotherapy after incomplete tumor resection . further regression of the tumor was reported ( by the treating radiotherapists ) in three of them . another important issue to be cleared is whether meningiomas sometimes progress histopathologically to a higher grade and develop aggressiveness after they are operated . some series have shown that up to 2% of all benign meningiomas transform into malignant . this is supported by other studies also [ 3 , 7 ] , but other writers reject it . in our series , we had one patient with grade i meningioma which progressed to grade ii according to the histopathological result of the second resection . atypical and malignant meningiomas appear to be distinct entities with poor prognosis , despite the surgical intervention . radical tumor excision is the most effective treatment , as it determines the patient outcome , and it should always be applied . in cases of subtotal resection , radiotherapy should be applied , as it seems to delay tumor 's reappearance .
aim . to evaluate the frequency of atypical and malignant meningiomas and analyze recurrence rate ; to study the morbidity and mortality of these tumors compared to benign meningiomas 
 . methods . during 19922007 
 , 16 patients with malignant and 16 patients with atypical meningioma were operated in neurosurgery department of thessaloniki 's papanikolaou hospital . 
 we analyzed tumor histology , location , and extent of surgical resection with respect to tumor reappearance and patients ' outcome and compared the behavior of benign versus nonbenign meningiomas . 
 results . 
 malignant meningiomas accounted for 4.4% ( 16 patients ) and atypical meningiomas for another 4.4% of the series of patients ( 353 ) who were operated for intracranial meningioma at our department that period . 
 malignant meningiomas recurred at a rate of 75% and atypical meningiomas recurred at a rate of 41.6% . 
 there was a significant association of the histological classification ( benign , atypical , and malignant ) with recurrence ( p < 0.01 ) . 
 the recurrence rate after complete resection was 13.8% . 
 the recurrence rate for incomplete resection was 46.7% . 
 extent of tumor removal was significant to recurrence ( p 
 < 0.001 ) for benign as well for atypical and malignant meningiomas . 
 tumor location ( p > 0.05 ) was not significant to recurrence . conclusions . 
 atypical and malignant meningiomas appeared at a rate of 8.8% of our series of intracranial meningiomas . 
 they showed a significant predisposition to recur . 
 these rare subtypes have higher morbidity and mortality rates than benign meningiomas . 
 recurrence depends primarily on the extent of surgical removal and on the histological characterization of the tumor as atypical or malignant .