Answer: Meningioma

Histology: The lesion is characterized by a proliferation of relatively uniform spindle-shaped cells.

Discussion: Meningiomas typically occur in middle age women. They tend to involve the midline saginal sinus. Of note, even benign meingiomas may invade the skull and as illustrated in this case, into the scalp. In the scalp these lesions can be difficult to diagnoses if the entity is not considered.

Grossly, meningiomas are well-demarcated neoplasms that often have a gritty texture when cut. Histologically, as demonstrated in this case, they are typically cellular neoplasms in which the spindle-shaped cells tend to whirl sometimes around psamoma bodies. In difficult case, such as this, immunohistochemical stains can be performed. Meningiomas are positive for epithelial membrane antigen, vimentin and often progesterone receptor. Secretory meningiomas can express carcinoembryonic antigen.