MKI67 and pituitary gland adenoma: Although pituitary adenomas can be classified as invasive or noninvasive, typical or atypical, and aggressive or nonaggressive, these categorizations do not accurately describe malignant pituitary tumors without cerebrospinal and/or systemic metastasis that grow rapidly, have high Ki-67 indexes, recur frequently and early, are resistant to conventional treatments and/or salvage treatment with TMZ, and ultimately result in death.