Anaplastic meningioma (also known as malignant meningiomas) is defined by several criteria including:
1) Invasion of adjacent brain parenchyma or skull. (see invasive meningioma)
2) Numerous mitosis (> 5/high-powered field)
3) Elevated proliferative index (>3%) as assessed by either 5-bromodeoxyuridine or KI-67 staining
5) Increased cellularity
6) Nuclear pleomorphism
Anaplastic meningiomas are uncommon, accounting for only ~1% of all meningiomas 1).
Generally, it is not possible to confidently distinguish benign (WHO grade I) and atypical (WHO grade II) from anaplastic (WHO grade III) meningiomas on general morphology. The most reliable feature in suggesting a non-grade I tumour is the presence of lower ADC values (reflecting higher cellularity) 2) 3).
Importantly presence of vasogenic oedema in adjacent brain parenchyma is not a predictor of atypical or anaplastic histology 4).
Brain invasion, although by definition denoting at least a grade II tumour, is also surprisingly difficult to predict on MRI.
There are, some CT or MRI trends that point in favor of malignant meningioma:
1) the absence of visible calcium aggregates 5).
Malignant progression with accumulation of mutations in a benign meningioma can result in an atypical meningioma and/or anaplastic meningioma. Both tumors are difficult to manage and have high recurrence and poor survival rates. The extent of tumor resection and histological grade are the key determinants for recurrence.
Anaplastic meningiomas are aggressive tumors, with a median overall survival time of 15 months 9).
They have a higher rate of recurrence and metastasis accompanied by a significantly shorter survival rate compared to benign variants. Meningioma cancer stem cells (CSCs) have been previously shown to be associated with resistance and aggressiveness. However, the role they play in meningioma progression is still being investigated 10).
56 patients from the Department of Neurosurgery, Beijing Tiantan Hospital, Beijing, China underwent surgeries between December 2008 and January 2016. Postoperative pathology reports confirmed the diagnosis of AM. Prognostic factors and the management were analysed in this study. AM was then divided into two groups. One group was primary AM, the other group was secondary AM.
Of all the 56 AM patients, 31 were male and 25 were female (male to female ratio of 1.24:1). The 1-, 3-, and 5-year progression-free survival (PFS) rates were 78.6%, 41.1% and 29.7%, respectively, and the corresponding overall survival (OS) rates were 82.1%, 50.1% and 45.0%, respectively. Homogeneous contrast might be a potential better prognostic factor for PFS (HR = 1.824, P = 0.083). Treatment with postoperative radiotherapy (PRT) was significantly associated with longer PFS (HR = 0.390, P = 0.007) and OS (HR = 0.376, P = 0.008) according to univariate analysis. Gross-total resection (GTR) was a favourable factor for PFS (HR = 2.059, P = 0.035) and OS (HR = 2.802, P = 0.004).
Achieving GTR is a favourable treatment strategy for patients with AM in this study and patients receiving postoperative radiotherapy (PRT) after resection is essential 11).
A study aimed at examining associations between patient and tumor-related factors and tumor-related death in patients with Atypical meningioma and anaplastic meningiomas (AAM) .
Garzon-Muvdi et al., conducted a population-based cohort study utilizing prospectively collected data from the Surveillance, Epidemiology, and End Results (SEER) database. Patients with diagnosis of AAM from 1973 to 2012 in the SEER database were included. Patients lacking clinical information were excluded. Multivariate analysis between patient and lesion characteristics, and AAM-related death was performed to adjust for confounding factors. We identified and included 522 patients in our study. Mean age at diagnosis was 60.8 ± 15.7 years. The majority of patients were White(73%), 15.5% Black, and 9.8% Asian. Average tumor size was 48.2 ± 20.3 mm. The tumor was locally confined in 57.1%, whereas it had intracranial extension in 29.3%, and extracranial extension in 8.8% of patients. The vast majority (94.8%) of tumors were supratentorial. Gross total resection (GTR) was documented in 65.5% of patients. Age at diagnosis (p = 0.001), tumor size (p = 0.003), surgery result (GTR vs. subtotal resection, p = 0.027), and radiation therapy (p = 0.2) were found to be significantly different between the comparison groups. In a multivariate proportional competing risk regression analysis age (HR 1.03, CI [1.01,1.04], p < 0.001), infratentorial location (HR 2.81, CI [1.20, 6.56], p = 0.017), tumor size (HR 1.01, CI [1.00,1.02], p = 0.032),and radiation treatment (HR 1.52, CI [1.11, 2.09], p = 0.01) were significantly associated with tumor-related death. The association of age at diagnosis, tumor size, location, and radiotherapy with overall survival in patients with AAM is demonstrated. The results provide a context for individualized treatment plans in patients with AAM. Additional studies focusing on issues such as the use of radiation and chemotherapy will clarify the best modality to achieve disease control 12).
Baeesa et al. from the Division of Neurosurgery, Department of Surgery, King Abdulaziz University Hospital, Faculty of Medicine, Jeddah, Saudi Arabia, report a 29-year-old man who underwent a resection of a grade I meningioma in 2011. The patient had multiple local recurrences of the tumor that exhibited an aggressive change in behavior and transformation to grade III meningioma and developed extracranial metastasis to the cervical spine. He underwent multiple operations and received radiotherapy. Analysis of the meningioma indicated the presence of CSCs markers before metastasis and showed elevated expressions of associated markers in the metastasized tissue. Also, and similar to the patient's profile, the pharmacological testing of a primary cell line retrieved from the metastasized tissues showed a high level of drug tolerance and a loss of ability to initiate apoptosis.
Malignant progression of grade I meningioma can occur, and its eventuality may be anticipated by detecting CSCs. We included a comprehensive literature review of relevant cases and discussed the clinical, diagnostic and management characteristics of the reported cases 13).
A patient had an intracranial malignant meningioma and developed a symptomatic osteolytic contrast-enhancing lesion in the left C-1 lateral mass suspicious for metastasis. The authors performed a minimally invasive posterior resection of the lesion with vertebroplasty of C-1. Histopathology verified metastasis of the malignant meningioma. The surgical procedure resulted in prompt and permanent pain reduction until the patient died 18 months later. Given the very limited life expectancy in this case, the authors did not consider occipitocervical fusion because of their desire to preserve the range of motion of the head. Therefore, they suggest minimally invasive tumor resection and vertebroplasty in selected palliative tumor patients 14).