Feline intracranial meningioma with skull erosion and tumour extension into an area of skull hyperostosis

Abstract

Skull hyperostosis is a frequently recognised feature of meningioma in feline and human patients, occurring at a frequency of around 4.5% of human cases. Evidence of osteolysis with extension of meningioma into, and in some cases through, the region of skull hyperostosis is much less commonly described in human patients. Here we present a 12-year-old cat with marked skull hyperostosis secondary to an intracranial meningioma, with magnetic resonance imaging and computed tomography evidence of tumour extension into the skull, centrally within the region of hyperostosis. Only a thin layer of bone was remaining between the mass and the extracranial region. Surgical resection of the region of skull demonstrating tumour invasion and the underlying mass resulted in good resolution of clinical signs and no post-surgical recurrence of meningioma within the 5 months follow-up period. Histopathological examination confirmed the mass to be fibroblastic meningioma.

Fig 1

Skull hyperostosis secondary to intracranial meningioma with skull invasion by tumour tissue. (A) Rostrocaudal skull radiograph demonstrating hyperostosis of the skull on the right, with skull erosion correlating to the location of the tumour (arrows). Transverse pre-contrast CT scan (B) and 3-dimensional CT reconstruction (C) through the level of the tumour demonstrating marked skull hyperostosis, with skull erosion and invasion of tumour into the region of hyperostosis (arrows). Pre- (D) and post-contrast (E) T1-weighted MR images demonstrating marked skull hyperostosis (arrow in D) and tumour invasion into the region of hyperostosis. There is homogenous enhancement of the extra-axial tumour mass, with a characteristic ‘dural tail’ (open arrow in E) consistent with the imaging appearance of a meningioma. Contrast enhancement is evident overlying the external surface of the skull (arrowheads), suggestive of local reaction (no evidence of tumour spread was evident on histopathology). (F) Haematoxylin and eosin-stained section following fixation and bone decalcification demonstrated the mass to be intimately associated with the overlying skull and invading a large cavity within the bone (Bar=1 mm). The mass was composed of streams and woven bundles of neoplastic spindle cells embedded within a collagenous matrix consistent with a fibroblastic meningioma (inset – bar=200 μm).