Clinical Implications of the Mitotic Index as a Predictive Factor for Malignant Transformation of Atypical Meningiomas

Objective

Intracranial atypical meningiomas have a poor prognosis and high rates of recurrence. Moreover, up to one-third of the recurrences undergo high-grade transformation into malignant meningiomas. We aimed to investigate the clinical factors that can predict the propensity of malignant transformation from atypical to anaplastic meningiomas.

Methods

Between 2001 and 2018, all patients with atypical meningioma, in whom the tumors had undergone malignant transformation to anaplastic meningioma, were included. The patients' medical records documenting the diagnosis of atypical meningioma prior to malignant transformation were reviewed to identify the predictors of transformation. The control group comprised 56 patients with atypical meningiomas who were first diagnosed between January 2017 and December 2018 and had no malignant transformation.

Results

Nine patients in whom the atypical meningiomas underwent malignant transformation were included. The median time interval from diagnosis of atypical meningioma to malignant transformation was 19 months (range, 7-78). The study group showed a significant difference in heterogeneous enhancement (77.8% vs. 33.9%), bone invasion (55.6% vs. 12.5%), mitotic index (MI; 14.8±4.9 vs. 3.5±3.9), and Ki-67 index (20.7±13.9 vs. 9.5±7.1) compared with the control group. In multivariate analysis, increased MI (odds ratio, 1.436; 95% confidence interval, 1.127-1.900; p=0.004) was the only significant factor for predicting malignant transformation.

Conclusion

An increased MI within atypical meningiomas might be used as a predictor of malignant transformation. Tumors at high risk for malignant transformation might require more attentive surveillance and management than other atypical meningiomas.

Endoscopic Endonasal Craniofacial Surgery for Recurrent Skull Base Meningiomas Involving the Pterygopalatine Fossa, the Infratemporal Fossa, the Orbit, and the Paranasal Sinus

OBJECTIVE

Skull base meningiomas carry a nonnegligible risk of recurrence. In particular, those arising from the sphenoid wings or middle cranial fossa penetrate into extracranial regions, uncommonly showing massive expansion into the craniofacial regions on recurrence. The role of endoscopic endonasal surgery for those intractable lesions remains unclear.

METHODS

We performed endoscopic endonasal craniofacial surgery for 8 recurrent meningiomas invading into the pterygopalatine fossa, infratemporal fossa, nasopharynx, paranasal sinus, or orbit, comprising 2 meningothelial and 1 fibrous meningiomas (World Health Organization [WHO] grade I), 3 atypical and 1 clear cell meningiomas (grade II), and 1 anaplastic meningioma (grade III). All were large (15-80 cm³; median, 45 cm³) and highly vascularized.

RESULTS

All 8 tumors were sufficiently resected. Gross total resection of the craniofacial part of the lesions was achieved in 5 patients (62.5%). In 3 patients with WHO grade I meningiomas and 1 with grade II, tumors were successfully controlled as of the last follow-up. In 4 patients with WHO grade II or III meningiomas, craniofacial lesions were controlled, whereas original intracranial lesions were poorly controlled and became critical.

CONCLUSIONS

We consider the endoscopic endonasal approach as an acceptable, less-invasive alternative for recurrent craniofacial meningioma. Although all these cases were relatively large and highly vascularized, preoperative endovascular embolization of the feeding arteries contributes to significantly reducing vascularity of the tumors, and local control of the craniofacial lesions was successfully achieved in all cases. Endoscopic endonasal craniofacial surgery enabled sufficient mass reduction without disfiguring facial incisions.

Anterior temporal chordoid meningioma causing compressive optic neuropathy

PURPOSE

Optic neuropathy associated with proptosis and ocular motility restrictions is suggestive of a compressive etiology. This raises concern for a mass lesion involving the orbit or orbital apex. Meningiomas, which account for 4% of all intraorbital tumors and 20 to 30% of all intracranial tumors, are capable of compressing critical anatomic structures within the orbit or orbital apex, and thereby impairing both afferent and efferent visual function. The purpose of this case report is to present a case of chordoid meningioma associated with compressive optic neuropathy.

METHODS

A 51-year-old woman presented with clinicopathological features pathognomonic of compressive optic neuropathy and orbital apex syndrome. Radiologic and neuropathologic evaluation revealed a large right anterior temporal atypical meningioma with chordoid features associated with frontal intraparenchymal edema. The therapeutic intervention consisted of orbitozygomatic craniotomy and radiotherapy.

RESULTS

Postoperatively, the patient progressed very well with considerable improvement of her visual and oculomotor function. The MIB-1 labeling index of 5 to 7% calls for close observation because of an increased probability of recurrence.

CONCLUSIONS

This case highlights the importance of prompt diagnosis and treatment, because chordoid meningiomas exhibit a more aggressive biological behavior, with the potential to cause significant morbidity because of mass effect and higher risk of recurrence. To our knowledge, this is the first report of a rare case of a chordoid meningioma in the anterior temporal lobe that presented as a compressive optic neuropathy. The details of this case are presented with a review of relevant literature.