Favorable Long-Term Outcomes of Chordoid Meningioma Compared With the Other WHO Grade 2 Meningioma Subtypes.

BACKGROUND: WHO grade 2 meningiomas, including atypical, chordoid, and clear cell subtypes, form a heterogenous group of meningiomas with varying aggressiveness and clinical behavior.

OBJECTIVE: To demonstrate the differences of clinical-histopathological characteristics and long-term outcomes among these 3 subtypes.

METHODS: A total of 609 consecutive patients diagnosed with WHO grade 2 meningiomas (543 atypical meningiomas [AMs], 36 chordoid meningiomas [CMs], and 30 clear cell meningiomas [CCMs]) from 2010 to 2018 were enrolled in this study. We compared the clinical-histopathological characteristics and long-term outcomes in these 3 subtypes and assessed survival differences among the subtypes. Targeted panel sequencing of meningioma-relevant genes was performed in the cases of CM.

RESULTS: The patients with CCM were significantly younger than those with AM (P < .001) and CM (P = .016). CMs were more likely to receive gross total resection than AMs and CCMs (P = .033). The Ki-67 index was lower (P < .001) while the progesterone receptors-positive rate was higher (P = .034) in CM than in AM and CCM. Importantly, survival analysis demonstrated that CM had better progression-free survival (P = .022) and overall survival (P = .0056) than non-CM tumors. However, the PFS of CM was still worse than WHO grade 1 meningiomas (P < .001). Alterations in NF2 (20.6%) and KMT2C (26.5%) were associated with poorer PFS in CM (P = .013 for NF2; P = .021 for KMT2C).

CONCLUSION: Patients with CM had better long-term postoperative outcomes than the other WHO grade 2 subtypes. A lower Ki-67 index, higher PR status, higher extent of resection, and lower frequency of NF2 alteration might contribute to favorable clinical outcomes of CM.