Malignant Pituitary Adenoma

The authors present 2 cases of malignant pituitary adenoma. One case has remote metastases to the right frontal lobe, and the other case has invasion into the adjacent temporal lobe and malignant features histologically. Malignant pituitary adenoma constitute less than 1% of the large reported series of pituitary adenoma, which defined as (1) it burst its capsule to invade the adjacent nervous structures or bone, (2) it shows malignant features histologically, such as frequent mitoses, anaplasia with hyperchromatic pleomorphic cells, loss of alveolar arrangement, and (3) presence of distant metastases.