Review of Atypical and Anaplastic Meningiomas: Classification, Molecular Biology, and Management

Abstract

Although the majority of meningiomas are slow-growing and benign, atypical and anaplastic meningiomas behave aggressively with a penchant for recurrence. Standard of care includes surgical resection followed by adjuvant radiation in anaplastic and partially resected atypical meningiomas; however, the role of adjuvant radiation for incompletely resected atypical meningiomas remains debated. Despite maximum treatment, atypical, and anaplastic meningiomas have a strong proclivity for recurrence. Accumulating mutations over time, recurrent tumors behave more aggressively and often become refractory or no longer amenable to further surgical resection or radiation. Chemotherapy and other medical therapies are available as salvage treatment once standard options are exhausted; however, efficacy of these agents remains limited. This review discusses the risk factors, classification, and molecular biology of meningiomas as well as the current management strategies, novel therapeutic approaches, and future directions for managing atypical and anaplastic meningiomas.

Keywords: WHO grade II meningioma; WHO grade III meningioma; anaplastic meningioma; atypical meningioma; high grade meningiomas (HGMs).

Figure 1

Histopathology of Atypical Meningiomas. Atypical meningioma (WHO grade II). (A) H&E staining, ×400 magnification, demonstrating cell sheeting. (B) H&E staining, ×200 magnification, demonstrating whorls, and early focus of degeneration. (C) H&E staining, ×200 magnification, demonstrating necrosis. (D) Ki67 staining, ×400 magnification, demonstrating proliferation indices. (E) H&E staining, ×400 magnification, demonstrating brain invasion.

Figure 2

Histopathology of Anaplastic Meningiomas. Anaplastic meningioma (WHO grade III). (A) H&E staining, ×200 magnification. (B) H&E staining, ×400 magnification, demonstrating mitoses >20 per high powerfield. (C) H&E staining, ×200 magnification, demonstrating frank necrosis. (D) Ki67 staining, ×400 magnification, demonstrating proliferation indices. (E) EMA staining, ×200 magnification.

Figure 3

Summary of management strategies for atypical and anaplastic meningiomas. ^*GTR, Gross total resection; STR, Subtotal resection; Dotted line represents lack of consensus regarding serial monitoring vs. adjuvant radiation following complete resection of WHO grade II meningioma.