An expansile lytic and sclerotic bone lesion is centered in the right parietal bone. The lesion measures 8 cm in maximal diameter. The lesion extends anteriorly just beyond the coronal suture into the right frontal bone and inferiorly to the squamosal suture. The involved outer table is irregular and the inner table is spiculated. The lesion is associated with enhancing soft tissue that extends laterally about 3 mm into the adjacent scalp under the temporalis muscle and medially about 1 cm into the epidural space.
There is evidence of mild mass effect with mild effacement of the sulci in the adjacent right posterior frontal lobe. There is no underlying edema pattern or midline shift. Cortical veins overlie this region and may be partially encased by the soft tissue component.
Together with the long duration of symptoms, the appearance favors intraosseous meningioma, perhaps of a higher grade given the degree of bony erosion. Cavernous hemangioma is an alternative consideration but this lesion typically spares the inner table, which is involved on the current study. Fibrous dysplasia, which relatively rarely involves the calvaria, is unlikely because it typically preserves the inner and outer tables even when it causes osseous expansion. More malignant etiologies such as lymphoma and metastases, despite the restricted diffusion seen on MRI, are felt to be unlikely given the hyperostotic component and long duration of symptoms. Osteosarcoma is also unlikely given the long course.