Clinicopathologic Features of Convexity en Plaque Meningioma.

BACKGROUND

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 clinicopathologic features of convexity meningioma en plaque.

METHODS

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 clinicopathologic features and treatment outcomes between the groups.

RESULTS

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), greater 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 5-year progression-free survival rates were 83% for the normal type and 38% for the en plaque type (log-rank test, P < 0.0001).

CONCLUSIONS

Convexity en plaque meningioma had a significantly greater recurrence rate than the normal type, largely attributable to the lower total removal rate. Close surveillance is suggested to be warranted in patients with convexity en plaque meningioma.