The imaging features favor a meningioma with a more aggressive behavior, given the extension into the right frontal sinus and the ill-defined margins with the adjacent brain suggesting invasion. 

MACROSCOPIC DESCRIPTION: 1. "Brain tissue": A piece of firm pink/tan tissue 10x8x3mm. All for frozen section/smear. 2. "Frontal tumor": Firm brown tissue 80x65x20mm with frond-like areas. No necrosis is seen.

MICROSCOPIC DESCRIPTION: 1&2. Sections show a moderately cellular meningioma with a well- developed meningothelial architecture. Tumor cells demonstrate uniform nuclear features. Scattered psammoma bodies are present. No mitoses or areas of necrosis are identified. There are multiple foci of brain invasion present. Dural attachment is noted.

DIAGNOSIS: 1&2. Brain, right frontal lobe tumor, resection: Typical meningothelial meningioma, with brain invasion (WHO Grade II).