Atypical Meningiomas: Histologic and Clinical Factors Associated With Recurrence

Atypical meningioma is a heterogeneous group of tumors with an unpredictable behavior. Our objectives were to study patients with atypical meningioma, monitor their follow-up, identify the histologic characteristics, and analyze factors associated with severe outcomes.

This retrospective study involved 28 patients with atypical meningioma from 1994 to 2014. The histologic samples were reviewed under current criteria. The association with recurrence and survival was analyzed statistically for clinical, therapeutic, histologic, and molecular factors.

The average age at the time of diagnosis was 55.5 years (range, 18-83 years) and 57% were female. Total resection (Simpson grade I) was performed in 10 cases (38%). Adjuvant radiotherapy was given to 13 patients. During the 77-month follow-up, 64% had a recurrence or progression. The average time to first recurrence and overall survival were 43.83 months and 149 months, respectively. Recurrence was found in 85% of the patients whose samples presented necrosis. Of the tumors, 84% showed a high mitotic index (4-20 mitoses/10 high-power field). Of the 4 patients with a low mitotic index (<4 mitoses/10 high-power field), the degree of resection was subtotal and 3 experienced disease progression. Of patients with Ki67 >9.9%, 67% had recurrence. The degree of resection was the only variable significantly associated with tumor recurrence.

The high rate of recurrence observed and the short disease-free survival exemplify the unpredictable behavior of atypical meningiomas. Total resection was the only significant factor associated with recurrence. However, the presence of atypical features, such as necrosis or high Ki67, is frequent in patients with disease progression.