The histopathological diagnosis of atypical meningioma: glass slide versus whole slide imaging for grading assessment

Abstract

Limited studies on whole slide imaging (WSI) in surgical neuropathology reported a perceived limitation in the recognition of mitoses. This study analyzed and compared the inter- and intra-observer concordance for atypical meningioma, using glass slides and WSI. Two neuropathologists and two residents assessed the histopathological features of 35 meningiomas-originally diagnosed as atypical-in a representative glass slide and corresponding WSI. For each histological parameter and final diagnosis, we calculated the inter- and intra-observer concordance in the two viewing modes and the predictive accuracy on recurrence. The concordance rates for atypical meningioma on glass slides and on WSI were 54% and 60% among four observers and 63% and 74% between two neuropathologists. The inter-observer agreement was higher using WSI than with glass slides for all parameters, with the exception of high mitotic index. For all histological features, we found median intra-observer concordance of ≥ 79% and similar predictive accuracy for recurrence between the two viewing modes. The higher concordance for atypical meningioma using WSI than with glass slides and the similar predictive accuracy for recurrence in the two modalities suggest that atypical meningioma may be safely diagnosed using WSI.

Keywords: Atypical meningioma; Digital; Recurrence; Reproducibility; Whole slide imaging.

Fig. 1

Atypical meningiomas captured on WSI. a Low-power view of an atypical meningioma, with its dural attachment. b Small cells with high nuclear/cytoplasmic ratio. c, d Brain invasion, with tongues of tumor cells infiltrating the brain parenchyma without intervening leptomeninges. e Sheeting with the absence of whorls or lobules. f Spontaneous necrosis showing gradual transition from the viable tumor, with a rim of pyknotic nuclei. g Mitosis in a squared cell corresponding to a field of 0.16 mm². h Macronucleoli

Fig. 2

Classification of meningiomas as atypical for major criteria, atypical for only minor criteria, and not atypical, by four observers on glass slides and WSI. All observers classified a higher percentage of cases as atypical for major criteria, and a lower one as not atypical, on WSI compared to glass slide

Fig. 3

Inter-observer concordance for histopathological features required for meningioma grading on glass slide and WSI. Inter-observer concordance was higher on WSI than on glass slides, for all parameters with the exception of high mitotic index

Fig. 4

Concordance between senior pathologists for histopathological features required for meningioma grading on glass slide and WSI. Inter-observer concordance was higher on WSI than on glass slides, for all parameters with the exception of high mitotic index

Fig. 5

Intra-observer concordance for atypical meningioma and individual histopathological parameters between glass slide and WSI. For all four observers, high mitotic index had the lowest intra-observer concordance