CT scan shows a left fronto-parietal 4 cm mass with calvarian invasion and adjacent mass effect. The patient did not actually have a pumpkin-shaped head. Rather, our program stretched the image to fit the frame.
A smear demonstrates cells with delicate chromatin pattern and indistinct cell borders.
Some of the cells have prominent nucleoli.
The frozen section demonstrates a diffuse growth pattern. Note that the histologic features of an atypical meningioma may be patchy and thus, thorough sampling is required.
The lesion is mitotically active (10 per 10 HPF) with high nuclear to cytoplasmic ratios and prominent nucleoli.
Strong reactivity for EMA is seen. Meningiomas show dual epithelial and mesenchymal differentiation and approximately 80% of these tumors are positive for EMA.
Ki67 labeling is estimated at 8-10%
A second case demonstrates a meningioma arising from the sphenoid ridge.
The tumor cells form whorls and exhibits increased cellularity.
Again, the tumor was mitotically active. Nuclei are oval with some central clearing.
Inclusions can be seen in some of the neoplastic cells.
Elevated Ki67 labeling can be appreciated.
Atypical menginiomas have higher rates of recurrence and more aggressive behavior compared to classic meningiomas. The diagnostic criteria includes high mitotic activity (defined as greater than 4 mitotic figures per 10 HPF) and at least three of the following features: sheet-like growth pattern, macronucleoli, small cell with high nuclear/cytoplasmic ratios, hypercellularity, brain invasion, and necrosis (Kumar, Prayson).
These features may be seen in any of the histologic variants. Along with chordoid and clear cell meningiomas, atypical meningiomas are categorized as WHO Grade II tumors. The increased mitotic rate can be visualized by Ki-67 labeling, which is usually around 7% (compared to 4% in WHO Grade I tumors)(Fletcher).
Fletcher CDM, ed. Diagnostic Histopathology of Tumors. 3rd Ed. Philadelphia, PA: Elsevier; 2007: 1707-1710.
Kumar V, Abbas AK, Fausto N. Robbins and Cotran Pathologic Basis of Disease. 7th Ed. Philadelphia, PA: Elsevier; 2005: 1409-1410
Prayson, RA. Neuropathology: Foundations in Diagnostic Pathology. Philadelphia, PA: Elvesier; 2005: 489-494.