Firm, rubbery, round or globular, these tumors compress the brain parenchyma. They may produce osteolytic or osteoblastic lesions in the bone. Histopathologically, the meningothelial cells are arranged in whorls. A common site is the acoustic nerve-roots. The tumor is encapsulated and, when it affects the acoustic nerve roots, is located in the cerebello-pontine angle.
Pituitary adenoma arises as a small nodule in the anterior pituitary gland.
Early detection is possible by MRI and enzyme assay. It is a cystic tumor situated in the sellar or suprasellar region and may extend into the third ventricle. The sold part of the tumor forms small nodules in the cyst wall.