Answer: Secretory meningioma

Histology: The tumor is composed of ovoid cells, which form sheets and whorls typical of meningioma. Intranuclear inclusions are abundantly evident. In addition, there are hyaline globules surrounded by the lesional cells. The tumor cells adjacent to these globules stain intensely for cytokeratin and CEA, a feature that is not typical of usual meningioma but characteristic of this variant, secretory meningioma.

Discussion: Metastatic carcinoma and melanoma which show far more pleomorphism than the current lesion. Focal cytokeratin immunoreactivity would be unusual in a carcinoma, which should be uniformly positive. Melanoma would label for S100 protein and not for EMA as the current lesion does. Melanoma should also not label for cytokeratin. Hemangiopericytoma would show a more consistent staghorn vascular pattern throughout the lesion and should not label diffusely for EMA, or focally for cytokeratin and CEA as the current case.

Secretory meningioma is a well-accepted variant of meningioma, which is considered Grade 1 under the WHO classification. Grade 1 meningiomas cannot show brain invasion, over 4 mitoses per 10 high power fields or chordoid, rhabdoid, clear cell or papillary patterns. Grade 2 meningiomas (atypical meningioma) are defined by either brain invasion, greater than 4 mitoses per 10 high power fields, chordoid or clear cell patterns, or three out of four of the following: high cellularity small cells, prominent nucleoli, and sheet-like growth pattern. Grade 3 meningiomas (malignant meningioma) are defined by greater than 2 mitoses per high power field, anaplasia (the tumor looks like a carcinoma, melanoma or sarcoma), or rhabdoid or papillary histology.