Answer: Meningioma

Histology: The surface epithelium is intact. The subepithelium is infiltrated by whorls of epithelioid cells with eosinophilic cytoplasm and oval nuclei. Pale intranuclear inclusions are readily identified. Delicate blood vessels are collared by zones of collagen. The tumor cells are not immunoreactive for EMA, CD34, actin or FXIIIa; but they are immunoreactive for progesterone receptor.

Discussion: Meningioma of the nasal cavity may either represent a primary extracranial meningioma or an intracranial tumor with extracranial extension. Most represent true extracranial tumors, but correlation with the clinical and radiographic findings is necessary to make the distinction. The nasal meningiomas retain the histopathologic features of their intracranial counterparts including morphologic variability as a function of histologic subtypes (e.g. fibroblastic, meningotheliomatous, psammomatous). Accordingly, they are usually easy to diagnose provided that they are included in the differential diagnosis of intranasal masses. If there is any uncertainty, immunohistochemistry can be used to confirm the diagnosis. Nasal meningiomas are typically immunoreactive for EMA and non-immunoreactive for cytokeratin, S100, CD34 or FXIIIa. In the exceptional case of an EMA-negative meningioma, positive nuclear staining for progesterone stain helps support the diagnosis. The extent of surgery for the removal of nasal meningiomas depends on the size of the tumor and the presence of any intracranial component.