LAUSR

The close geographic association of two or more synchronous primary brain tumors is an unusual occurrence. There are around 50 case reports of these intracranial collision tumors, mostly consisting of malignant astrocytoma (mainly glioblastoma) and meningioma. We present a rare intracranial collision tumor consisting of anaplastic ependymoma and atypical meningioma. To our knowledge, this is the first reported case of intracranial collision tumor with this combination. The patient is a 33-year-old gentleman who presented 2 years ago with new-onset intermittent headaches with increasing severity and associated blurry vision and vomiting. On imaging, he was found to have a 4.2 × 4.1 × 4.1-cm cystic-solid and heterogeneously enhancing extra-axial mass lesion in the left frontal lobe, with an enhancing dural tail. Histologic examination of the surgically excised lesion showed two geographically distinct areas of an extra-axial atypical meningioma (World Health Organization grade II) and an intra-axial anaplastic ependymoma (World Health Organization grade III). The anaplastic ependymoma component showed increased cellularity, pseudorosettes, microvascular proliferation, necrosis, and increased mitoses. It was diffusely positive for GFAP and had a Ki-67 proliferation index of 40%. The atypical meningioma showed 5 mitoses per 10 high-power fields. It had a membranous EMA immunoreaction and a Ki-67 proliferation index of approximately 20%. Recently, the patient had a recurrence of the anaplastic ependymoma component only. So far, no clear explanation has been found in the literature to understand the mechanisms leading to collision tumors. Since our patient does not appear to have any syndrome, it may represent a sporadic phenomenon; however, the sharing of a common oncogenic insult or any underlying molecular/genetic mechanism leading to synchronous tumorigenesis remains to be elucidated in this case.