The pathology of non-functional pituitary adenomas.

Pituitary adenomas encompass the endocrine, symptomatic or functionally active and the non-functional, null cell or functionally inactive. According to their sizes, they can be very small, also called microadenomas, or they can be very large, "invasive", or macroadenomas usually without clinical evidence of hypersecretion. The "invasive" pituitary adenomas usually grow beyond the confines of the sella turcica. These adenomas are characterized anatomically by displacement, distortion and compression of the adjacent sellar structures. They may destroy bone and penetrate into the nasal cavity or into the cavernous sinuses. They may distend the diaphragm sella and compress the hypothalamus and the optic chiasm and optic tracts or they may distort the cerebral cortex or penetrate into the third ventricle. "Invasive" pituitary adenomas are characterized clinically by visual disturbances, headaches, seizures, diabetes insipidus and by hypothalamic dysfunction mimicking some endocrinologically active pituitary adenomas. The diagnosis of invasive pituitary adenomas can be suspected clinically and can be confirmed by radiological evidence of destruction of the sella turcica and its boundaries or by neurosurgical intervention and finally by necropsy findings of "invasion" of the parasellar and suprasellar structures.