Malignant tumors in the pituitary gland.

Malignant tumors of the pituitary gland may mimic pituitary adenomas both in clinical presentation and in imaging, and often present with neurologic findings including visual field loss and extraocular movement palsies. We describe a 58-year-old woman without known malignancy who presented with extraocular movement weakness, loss of facial sensation, and a sellar plasmacytoma; a 49-year-old woman with oculomotor palsy, no known malignancy, and rapidly failing vision who had metastatic lung carcinoma; and a 70-year-old woman with metastatic breast carcinoma who presented with rapidly failing vision and a metastasis to the anterior lobe of the pituitary. These cases illustrate several important features of malignancy in the pituitary fossa: that it can mimic a "nonfunctioning" pituitary adenoma in clinical presentation and imaging; that rapidly progressive visual loss, extraocular movement palsies, or facial sensory loss may help to distinguish it from a benign adenoma; and that when the pathologist evaluates an alleged "nonsecretory" or "nonfunctional" adenoma, metastases should be included in the differential diagnosis.