Convexity En Plaque Meningioma Manifesting as Subcutaneous Mass: Case Report

A 67-year-old woman sensed a slowly growing, painless hard mass in the left parietal region. Cranial computed tomography showed focal bony erosion and homogeneous sclerotic change at the affected site. Magnetic resonance (MR) imaging revealed an enhanced subcutaneous mass and irregularly thickened dura mater. Intraoperatively, the subcutaneous tumor was found to be strongly adhered to the temporalis muscle. The outer table was eroded adjacent to the subcutaneous tumor, whereas the bony structures of the inner table were intact. The dura mater underneath had irregular-shaped, yellowish convolutions both on the outer and inner surfaces. The patient underwent total tumor resection with sufficient normal margins. The histological diagnosis was World Health Organization (WHO) grade I meningioma, with finger-like outward extensions through the dura mater and overlying skull, and infiltration among into the temporalis muscle fibers. Meningiomas may form a subcutaneous mass without intracranial growth.