Malignant myoepithelioma of cranial dura.

Malignant tumors of myoepithelial origin have been increasingly recognized at a variety of sites. Herein, we describe an example of malignant myoepithelioma arising in intracranial dura. The patient is a 47-year-old woman who presented with intracranial hemorrhage and on magnetic resonance imaging was found to have an enhancing tumor. No extracranial primary tumor was identified. A gross total resection was performed. Histologically, it varied in pattern from diffuse to focally (<10%) ductular and consisted of epitheloid to spindle cells showing marked mitotic activity. Prominent infiltration of the dura was noted. Immunohistochemical stains showed convincing expression of cytokeratins (AE1/AE3 and CAM 5.2), S-100 protein, smooth muscle actin, and glial fibrillary acidic protein. Electron microscopy performed on formalin-fixed, paraffin-embedded tissue demonstrated cohesive cells with focal intermediate filament content and surface basal lamina formation at stromal interfaces. Occasional desmosomes with tonofilaments surrounded intercellular lumina containing masses of filamentous material. This example of malignant myoepithelioma is the first convincing primary salivary gland type tumor to arise in an intracranial location outside the sellar region or ear. Intracranial dura should be added to various sites at which this morphologically heterogenous tumor may arise.