Meningioma sampling: how much is enough for the accurate grading of atypical meningiomas?

Area of Science:

• Neuropathology
• Surgical Pathology
• Oncology

Background:

• Meningioma grading is crucial for patient management and prognosis.
• Current grading relies on specific pathological criteria and histopathological subtypes.
• These criteria can be focally present, posing challenges for accurate diagnosis.

Purpose of the Study:

• To compare meningioma grading parameters between periods with different tumor sampling techniques.
• To determine the probability of detecting grading criteria in entirely processed meningiomas.
• To establish optimal slide examination protocols for accurate meningioma grading.

Main Methods:

• Retrospective analysis of meningioma cases from two distinct time periods (2002-2008 and 2012-2018) with differing sampling protocols.
• Comparison of the frequency of grading parameters (mitotic count, small cell foci, etc.) between the two periods.
• Detailed examination of 59 entirely sampled grade 2 meningiomas to assess parameter distribution across slides.

Main Results:

• No significant difference in overall tumor grade frequency between the two sampling periods (p=0.17).
• Entire tumor sampling significantly increased the detection of mitosis (≥4/1.6mm²), small cell foci, macronucleoli, and hypercellularity (p<0.05).
• Examining at least six slides from entirely sampled meningiomas allows for correct grading in over 95% of cases.

Conclusions:

• Meningioma tumor sampling methodology significantly impacts the detection of key grading parameters.
• Standardizing and specifying sampling techniques in research is essential for reproducible meningioma grading.
• A minimum of six slides should be examined for accurate grading of entirely sampled meningiomas.