Polycystic and ring-shaped intracranial meningiomas.

Intracranial meningiomas may be associated with peritumoral, unilocular cysts. In two middle-aged women we have recently treated, CT scan revealed ring-shaped and polycistic tumors which proved to be meningiomas. This unusual aspect has previously received scant attention. In the first patient the cysts were intratumoral and the walls consisted entirely of meningiomatous tissue; in the second case the cysts were peritumoral and their connective walls contained scattered nests of tumor cells.