Clinicopathological features of convexity en plaque meningioma.

Abstract

En plaque meningioma is a rare subtype of meningioma that develops along the dura mater in a plate-like fashion and invades the bone. We examined the clinicopathological features of convexity meningioma en plaque. We conducted a retrospective, single-center cohort study of 81 cases of newly diagnosed convexity meningiomas operated upon at our hospital between 2009 and 2024. Convexity meningiomas were classified as 'normal type' or 'en plaque type' (attachment diameter ≥40 mm, thickness to attachment diameter ratio ≤0.5). We compared clinicopathological features and treatment outcomes between the groups. Of 81 patients, 67 had the normal type meningiomas (83%), and 14 had en plaque type meningiomas (17%). In univariate analysis, the en plaque type was associated with absence of cerebrospinal space on preoperative T2-weighted imaging (100% vs. 48%, p<0.001), lower total resection rate (29% vs. 89%, p<0.001), higher incidence of postoperative epilepsy (43% vs 15%, p=0.03), and poorer Karnofsky performance status at 30 days postoperatively (36% vs. 7.5% p=0.01). Histopathologically, the meningothelial subtype was more common in en plaque type (64 vs. 30%, p=0.03). The five-year progression-free survival rates were 83% for normal type and 38% for en plaque type (log rank test, p < 0.0001). Convexity en plaque meningioma had a significantly higher recurrence rate than the normal type, largely due to the lower total removal rate. Close surveillance is suggested to be warranted in patients with convexity en plaque meningioma.