Meningioma Dural Tail

A 62-year-old woman with a history of breast cancer presents with a 6-month history of progressive morning headaches and two episodes of focal seizures involving the left arm. MRI of the brain demonstrates a homogeneously enhancing extra-axial mass along the right frontal convexity with a broad dural attachment, inward buckling of the gray-white matter junction, and a CSF cleft separating the mass from underlying cortex. The structure marked **B** in the diagram—a linear tapering enhancement of thickened adjacent dura extending several centimeters from the mass margin—is best described as which of the following?