Despite the relatively high prevalence of meningiomas, only a few studies describe their epidemiology, analyze demographics, and investigate risk factors for developing such lesions.14 In this study we reported the clinical and demographics features for meningiomas in a Mexican population.
The 2016 World Health Organization (WHO) classification of tumors affecting the central nervous system (CNS) recognizes three grades of meningioma. In absolute numbers, those known as benign meningiomas (grade I) are much more common than borderline malignant or malignant meningiomas (grade II-III). 15, 16
The current global prevalence for meningiomas is estimated three times higher for females. Also is reported an incidence peak between 30 and 59 years old. It could be due to the influence of hormonal factors.2, 9 In this study, we obtained similar results in our population.
Also, there was a close correlation between the Simpson grade and the risk of recurrence.17 Here we reported a major recurrence (24.7%) for Simpson 2 meningiomas after surgical resection. Meanwhile, the recurrence was 6.8% for meningiomas Simpson I, 2 and 44.4% in the case of Simpson III. These results are slightly higher in comparison to the original results reported by Simpson. 13 It is known that subtotal resection (STR) often leads to progression and subsequently often to new invasive procedures. Consequently, gross total resection (GTR) has always been considered the aim to pursue. On the other hand, the increasing mean age of patients with meningiomas imposes less aggressive surgical interventions due to the risk of morbidity or injury to neurovascular structures in locations such as parasagittal, skull base, or tentorium.12, 18
In locations with low surgical risk, such as convexity, Simpson grade I resection should continue to be the main objective.12
In general, higher WHO grading has been associated with the poor prognosis of meningiomas. 19
World while, WHO grade III meningiomas show extremely aggressive behavior and high rates of recurrence.20 In our study, in accordance to the histological type, the microcystic meningiomas (WHO I) had a surveillance rate of 60 months (lowest) in contrast with transitional (WHO I) with 122 months (highest). For the non-graphed variants, not enough censored data were obtained, so no data was obtained from them. For the WHO grade classification, in our study, the most frequent was grade I. It is in accordance with current medical literature.2 Also, the Simpson grade II was the 40.8% of the postsurgical resection histopathological report, two times more in women than men.
Tumor recurrence after complete surgical resection could be due to local persistence of tumor cells with clonogenic capacity due to tumor seeding during surgery, microinvasion of lymphatic vessels and other tissues, or incomplete microscopic resection of the tumor.21Finally, the extent of surgical resection reflected by the Simpson grade seems to be closely associated with the risk of recurrence in association to the histological type. 17 For example WHO grade I tumors with features of atypia are more likely to progress than those without features of atypia.22 Recent Mexican papers lay the foundations for future studies on the differentiation and typing of meningiomas, regardless of the histological grade to which they belong.23 Tumor size, location, and bone infiltration were reported as prognostic factors although these factors were not associated with the poor prognosis of recurrent meningioma.17, 19
Strengths and Limitations of the Study
The strength of this study is that this is the one of the largest case series that analyzes postoperative survival in Mexican population. However, this study is limited by its retrospective nature. Our variables are just limited to the available data in the medical centers that participate in this job.