Necrosis is a consistent factor to recurrence of meningiomas: should it be a stand-alone grading criterion for grade II meningioma?

The purpose of this study was to evaluate spontaneous necrosis as a possible isolated factor for progression and recurrence in grade I meningiomas classified according to the current World Health Organization (WHO) classification. Meningiomas are the most frequently reported primary intracranial tumours, accounting for more than 35%. The 2016 WHO classification of central nervous system tumors stratifies meningiomas in grades I (benign), II (atypical), and III (malignant), according to histopathological aspects and the risk of progression or recurrence. Among 110 patients with intracranial meningiomas, 70 were WHO grade I meningiomas with no findings of atypia (G1WON), 15 were WHO grade I with necrosis (G1WN), 21 were WHO grade II (G2), and 4 were WHO grade III (G3). The mean follow-up was 5.9 ± 0.2 years. High performance scale (KPS ≥ 80) was different (p < 0.001) between WHO grade I meningiomas without (81.4%) and with (60%) necrosis. The 5-year mortality rate was 1.4, 6.7 and 5.9% for G1WON, G1WN and G2, respectively, with significant difference (p = 0.011) related to the presence of necrosis. The risk of recurrence was 3.7 times higher in G1WN than in G1WON (p = 0.017), and 4.2 times in G2 (p = 0.010). Progression-free survival (PFS) was clearly higher in patients with G1WON compared to G1WN and G2 (p = 0.002 and p < 0.001, respectively). There was no significant difference in PFS between G1WN and G2 (p = 0.692). Retreatment was also superior in meningioma with necrosis. Our findings provide clear statistical data to consider that patients with benign meningiomas and histologic findings of spontaneous necrosis are at increased risk of progression and recurrence compared to those with benign lesion without atypical features. Statistical analysis curves also suggest that these lesions behave more similarly to those currently classified as WHO grade II meningioma.